HTML Basic Examples

In this chapter we will show some basic HTML examples.

Don't worry if we use tags you have not learned about yet.

HTML Documents

All HTML documents must start with a document type declaration: <!DOCTYPE html>.

The HTML document itself begins with <html> and ends with </html>.

The visible part of the HTML document is between <body> and </body>.

Example

<!DOCTYPE html>
<html>
<body>

<h1>My First Heading</h1>
<p>My first paragraph.</p>

</body>
</html>

The <!DOCTYPE> Declaration

The <!DOCTYPE> declaration represents the document type, and helps browsers to display web pages correctly.

It must only appear once, at the top of the page (before any HTML tags).

The <!DOCTYPE> declaration is not case sensitive.

The <!DOCTYPE> declaration for HTML5 is:

<!DOCTYPE html>

HTML Headings

HTML headings are defined with the <h1> to <h6> tags.

<h1> defines the most important heading. <h6> defines the least important heading:

Example

<h1>This is heading 1</h1>
<h2>This is heading 2</h2>
<h3>This is heading 3</h3>

HTML Paragraphs

HTML paragraphs are defined with the <p> tag:

Example

<p>This is a paragraph.</p>
<p>This is another paragraph.</p>

HTML Links

HTML links are defined with the <a> tag:

Example

The link's destination is specified in the href attribute.

Attributes are used to provide additional information about HTML elements.

You will learn more about attributes in a later chapter.

HTML Images

HTML images are defined with the <img> tag.

The source file (src), alternative text (alt), width, and height are provided as attributes:

Example

How to View HTML Source

Have you ever seen a Web page and wondered "Hey! How did they do that?"

View HTML Source Code:

Right-click in an HTML page and select "View Page Source" (in Chrome) or "View Source" (in Edge), or similar in other browsers. This will open a window containing the HTML source code of the page.

Inspect an HTML Element:

Right-click on an element (or a blank area), and choose "Inspect" or "Inspect Element" to see what elements are made up of (you will see both the HTML and the CSS). You can also edit the HTML or CSS on-the-fly in the Elements or Styles panel that opens.

SQL Tutorial

SQL is a standard language for storing, manipulating and retrieving data in databases.

Our SQL tutorial will teach you how to use SQL in: MySQL, SQL Server, MS Access, Oracle, Sybase, Informix, Postgres, and other database systems.

Examples in Each Chapter

With our online SQL editor, you can edit the SQL statements, and click on a button to view the result.

Example

SELECT * FROM Customers;

Click on the "Try it Yourself" button to see how it works.

Introduction to SQL

SQL is a standard language for accessing and manipulating databases.

What is SQL?

SQL stands for Structured Query Language
SQL lets you access and manipulate databases
SQL became a standard of the American National Standards Institute (ANSI) in 1986, and of the International Organization for Standardization (ISO) in 1987

What Can SQL do?

SQL can execute queries against a database
SQL can retrieve data from a database
SQL can insert records in a database
SQL can update records in a database
SQL can delete records from a database
SQL can create new databases
SQL can create new tables in a database
SQL can create stored procedures in a database
SQL can create views in a database
SQL can set permissions on tables, procedures, and views

SQL is a Standard - BUT....

Although SQL is an ANSI/ISO standard, there are different versions of the SQL language.

However, to be compliant with the ANSI standard, they all support at least the major commands (such as SELECT, UPDATE, DELETE, INSERT, WHERE) in a similar manner.

Note: Most of the SQL database programs also have their own proprietary extensions in addition to the SQL standard!

Using SQL in Your Web Site

To build a web site that shows data from a database, you will need:

An RDBMS database program (i.e. MS Access, SQL Server, MySQL)
To use a server-side scripting language, like PHP or ASP
To use SQL to get the data you want
To use HTML / CSS to style the page

RDBMS

RDBMS stands for Relational Database Management System.

RDBMS is the basis for SQL, and for all modern database systems such as MS SQL Server, IBM DB2, Oracle, MySQL, and Microsoft Access.

The data in RDBMS is stored in database objects called tables. A table is a collection of related data entries and it consists of columns and rows.

Look at the "Customers" table:

Example

SELECT * FROM Customers;

Every table is broken up into smaller entities called fields. The fields in the Customers table consist of CustomerID, CustomerName, ContactName, Address, City, PostalCode and Country. A field is a column in a table that is designed to maintain specific information about every record in the table.

A record, also called a row, is each individual entry that exists in a table. For example, there are 91 records in the above Customers table. A record is a horizontal entity in a table.

A column is a vertical entity in a table that contains all information associated with a specific field in a table.

SQL Syntax

Database Tables

A database most often contains one or more tables. Each table is identified by a name (e.g. "Customers" or "Orders"). Tables contain records (rows) with data.

In this tutorial we will use the well-known Northwind sample database (included in MS Access and MS SQL Server).

Below is a selection from the "Customers" table:

CustomerID	CustomerName	ContactName	Address	City	PostalCode	Country
1	Alfreds Futterkiste	Maria Anders	Obere Str. 57	Berlin	12209	Germany
2	Ana Trujillo Emparedados y helados	Ana Trujillo	Avda. de la Constitución 2222	México D.F.	05021	Mexico
3	Antonio Moreno Taquería	Antonio Moreno	Mataderos 2312	México D.F.	05023	Mexico
4	Around the Horn	Thomas Hardy	120 Hanover Sq.	London	WA1 1DP	UK
5	Berglunds snabbköp	Christina Berglund	Berguvsvägen 8	Luleå	S-958 22	Sweden

The table above contains five records (one for each customer) and seven columns (CustomerID, CustomerName, ContactName, Address, City, PostalCode, and Country).

SQL Statements

Most of the actions you need to perform on a database are done with SQL statements.

The following SQL statement selects all the records in the "Customers" table:

Example

SELECT * FROM Customers;

In this tutorial we will teach you all about the different SQL statements.

Keep in Mind That...

SQL keywords are NOT case sensitive: select is the same as SELECT

In this tutorial we will write all SQL keywords in upper-case.

Semicolon after SQL Statements?

Some database systems require a semicolon at the end of each SQL statement.

Semicolon is the standard way to separate each SQL statement in database systems that allow more than one SQL statement to be executed in the same call to the server.

In this tutorial, we will use semicolon at the end of each SQL statement.

Some of The Most Important SQL Commands

SELECT - extracts data from a database
UPDATE - updates data in a database
DELETE - deletes data from a database
INSERT INTO - inserts new data into a database
CREATE DATABASE - creates a new database
ALTER DATABASE - modifies a database
CREATE TABLE - creates a new table
ALTER TABLE - modifies a table
DROP TABLE - deletes a table
CREATE INDEX - creates an index (search key)
DROP INDEX - deletes an index

The SQL SELECT Statement

The SELECT statement is used to select data from a database.

The data returned is stored in a result table, called the result-set.

SELECT Syntax

SELECT column1, column2, ...
FROM table_name;

Here, column1, column2, ... are the field names of the table you want to select data from. If you want to select all the fields available in the table, use the following syntax:

SELECT * FROM table_name;

Demo Database

Below is a selection from the "Customers" table in the Northwind sample database:

CustomerID	CustomerName	ContactName	Address	City	PostalCode	Country
1	Alfreds Futterkiste	Maria Anders	Obere Str. 57	Berlin	12209	Germany
2	Ana Trujillo Emparedados y helados	Ana Trujillo	Avda. de la Constitución 2222	México D.F.	05021	Mexico
3	Antonio Moreno Taquería	Antonio Moreno	Mataderos 2312	México D.F.	05023	Mexico
4	Around the Horn	Thomas Hardy	120 Hanover Sq.	London	WA1 1DP	UK
5	Berglunds snabbköp	Christina Berglund	Berguvsvägen 8	Luleå	S-958 22	Sweden

SELECT Column Example

The following SQL statement selects the "CustomerName" and "City" columns from the "Customers" table:

Example

SELECT CustomerName, City FROM Customers;

SELECT * Example

The following SQL statement selects all the columns from the "Customers" table:

Example

SELECT * FROM Customers;

The SQL SELECT DISTINCT Statement

The SELECT DISTINCT statement is used to return only distinct (different) values.

Inside a table, a column often contains many duplicate values; and sometimes you only want to list the different (distinct) values.

SELECT DISTINCT Syntax

SELECT DISTINCT column1, column2, ...
FROM table_name;

Demo Database

Below is a selection from the "Customers" table in the Northwind sample database:

CustomerID	CustomerName	ContactName	Address	City	PostalCode	Country
1	Alfreds Futterkiste	Maria Anders	Obere Str. 57	Berlin	12209	Germany
2	Ana Trujillo Emparedados y helados	Ana Trujillo	Avda. de la Constitución 2222	México D.F.	05021	Mexico
3	Antonio Moreno Taquería	Antonio Moreno	Mataderos 2312	México D.F.	05023	Mexico
4	Around the Horn	Thomas Hardy	120 Hanover Sq.	London	WA1 1DP	UK
5	Berglunds snabbköp	Christina Berglund	Berguvsvägen 8	Luleå	S-958 22	Sweden

SELECT Example Without DISTINCT

The following SQL statement selects all (including the duplicates) values from the "Country" column in the "Customers" table:

Example

SELECT Country FROM Customers;

Now, let us use the SELECT DISTINCT statement and see the result.

SELECT DISTINCT Examples

The following SQL statement selects only the DISTINCT values from the "Country" column in the "Customers" table:

Example

SELECT DISTINCT Country FROM Customers;

The following SQL statement lists the number of different (distinct) customer countries:

Example

SELECT COUNT(DISTINCT Country) FROM Customers;

Note: The example above will not work in Firefox! Because COUNT(DISTINCT column_name) is not supported in Microsoft Access databases. Firefox is using Microsoft Access in our examples.

Here is the workaround for MS Access:

Example

SELECT Count(*) AS DistinctCountries
FROM (SELECT DISTINCT Country FROM Customers);

The SQL WHERE Clause

The WHERE clause is used to filter records.

It is used to extract only those records that fulfill a specified condition.

WHERE Syntax

SELECT column1, column2, ...
FROM table_name
WHERE condition;

Note: The WHERE clause is not only used in SELECT statements, it is also used in UPDATE, DELETE, etc.!

Demo Database

Below is a selection from the "Customers" table in the Northwind sample database:

CustomerID	CustomerName	ContactName	Address	City	PostalCode	Country
1	Alfreds Futterkiste	Maria Anders	Obere Str. 57	Berlin	12209	Germany
2	Ana Trujillo Emparedados y helados	Ana Trujillo	Avda. de la Constitución 2222	México D.F.	05021	Mexico
3	Antonio Moreno Taquería	Antonio Moreno	Mataderos 2312	México D.F.	05023	Mexico
4	Around the Horn	Thomas Hardy	120 Hanover Sq.	London	WA1 1DP	UK
5	Berglunds snabbköp	Christina Berglund	Berguvsvägen 8	Luleå	S-958 22	Sweden

WHERE Clause Example

The following SQL statement selects all the customers from the country "Mexico", in the "Customers" table:

Example

SELECT * FROM Customers
WHERE Country='Mexico';

Text Fields vs. Numeric Fields

SQL requires single quotes around text values (most database systems will also allow double quotes).

However, numeric fields should not be enclosed in quotes:

Example

SELECT * FROM Customers
WHERE CustomerID=1;

Operators in The WHERE Clause

The following operators can be used in the WHERE clause:

Operator	Description	Example
=	Equal
>	Greater than
<	Less than
>=	Greater than or equal
<=	Less than or equal
<>	Not equal. Note: In some versions of SQL this operator may be written as !=
BETWEEN	Between a certain range
LIKE	Search for a pattern
IN	To specify multiple possible values for a column

The SQL ORDER BY Keyword

The ORDER BY keyword is used to sort the result-set in ascending or descending order.

The ORDER BY keyword sorts the records in ascending order by default. To sort the records in descending order, use the DESC keyword.

ORDER BY Syntax

SELECT column1, column2, ...
FROM table_name
ORDER BY column1, column2, ... ASC|DESC;

Demo Database

Below is a selection from the "Customers" table in the Northwind sample database:

CustomerID	CustomerName	ContactName	Address	City	PostalCode	Country
1	Alfreds Futterkiste	Maria Anders	Obere Str. 57	Berlin	12209	Germany
2	Ana Trujillo Emparedados y helados	Ana Trujillo	Avda. de la Constitución 2222	México D.F.	05021	Mexico
3	Antonio Moreno Taquería	Antonio Moreno	Mataderos 2312	México D.F.	05023	Mexico
4	Around the Horn	Thomas Hardy	120 Hanover Sq.	London	WA1 1DP	UK
5	Berglunds snabbköp	Christina Berglund	Berguvsvägen 8	Luleå	S-958 22	Sweden

ORDER BY Example

The following SQL statement selects all customers from the "Customers" table, sorted by the "Country" column:

Example

SELECT * FROM Customers
ORDER BY Country;

ORDER BY DESC Example

The following SQL statement selects all customers from the "Customers" table, sorted DESCENDING by the "Country" column:

Example

SELECT * FROM Customers
ORDER BY Country DESC;

ORDER BY Several Columns Example

The following SQL statement selects all customers from the "Customers" table, sorted by the "Country" and the "CustomerName" column. This means that it orders by Country, but if some rows have the same Country, it orders them by CustomerName:

Example

SELECT * FROM Customers
ORDER BY Country, CustomerName;

ORDER BY Several Columns Example 2

The following SQL statement selects all customers from the "Customers" table, sorted ascending by the "Country" and descending by the "CustomerName" column:

Example

SELECT * FROM Customers
ORDER BY Country ASC, CustomerName DESC;

The SQL AND Operator

The WHERE clause can contain one or many AND operators.

The AND operator is used to filter records based on more than one condition, like if you want to return all customers from Spain that starts with the letter 'G':

Example

Select all customers from Spain that starts with the letter 'G':

SELECT *
FROM Customers
WHERE Country = 'Spain' AND CustomerName LIKE 'G%';

Syntax

SELECT column1, column2, ...
FROM table_name
WHERE condition1 AND condition2 AND condition3 ...;

AND vs OR

The AND operator displays a record if all the conditions are TRUE.

The OR operator displays a record if any of the conditions are TRUE.

Demo Database

The table below shows the complete "Customers" table from the Northwind sample database:

CustomerID	CustomerName	ContactName	Address	City	PostalCode	Country
1	Alfreds Futterkiste	Maria Anders	Obere Str. 57	Berlin	12209	Germany
2	Ana Trujillo Emparedados y helados	Ana Trujillo	Avda. de la Constitución 2222	México D.F.	05021	Mexico
3	Antonio Moreno Taquería	Antonio Moreno	Mataderos 2312	México D.F.	05023	Mexico
4	Around the Horn	Thomas Hardy	120 Hanover Sq.	London	WA1 1DP	UK
5	Berglunds snabbköp	Christina Berglund	Berguvsvägen 8	Luleå	S-958 22	Sweden
6	Blauer See Delikatessen	Hanna Moos	Forsterstr. 57	Mannheim	68306	Germany
7	Blondel père et fils	Frédérique Citeaux	24, place Kléber	Strasbourg	67000	France
8	Bólido Comidas preparadas	Martín Sommer	C/ Araquil, 67	Madrid	28023	Spain
9	Bon app'	Laurence Lebihans	12, rue des Bouchers	Marseille	13008	France
10	Bottom-Dollar Marketse	Elizabeth Lincoln	23 Tsawassen Blvd.	Tsawassen	T2F 8M4	Canada
11	B's Beverages	Victoria Ashworth	Fauntleroy Circus	London	EC2 5NT	UK
12	Cactus Comidas para llevar	Patricio Simpson	Cerrito 333	Buenos Aires	1010	Argentina
13	Centro comercial Moctezuma	Francisco Chang	Sierras de Granada 9993	México D.F.	05022	Mexico
14	Chop-suey Chinese	Yang Wang	Hauptstr. 29	Bern	3012	Switzerland
15	Comércio Mineiro	Pedro Afonso	Av. dos Lusíadas, 23	São Paulo	05432-043	Brazil
16	Consolidated Holdings	Elizabeth Brown	Berkeley Gardens 12 Brewery	London	WX1 6LT	UK
17	Drachenblut Delikatessend	Sven Ottlieb	Walserweg 21	Aachen	52066	Germany
18	Du monde entier	Janine Labrune	67, rue des Cinquante Otages	Nantes	44000	France
19	Eastern Connection	Ann Devon	35 King George	London	WX3 6FW	UK
20	Ernst Handel	Roland Mendel	Kirchgasse 6	Graz	8010	Austria
21	Familia Arquibaldo	Aria Cruz	Rua Orós, 92	São Paulo	05442-030	Brazil
22	FISSA Fabrica Inter. Salchichas S.A.	Diego Roel	C/ Moralzarzal, 86	Madrid	28034	Spain
23	Folies gourmandes	Martine Rancé	184, chaussée de Tournai	Lille	59000	France
24	Folk och fä HB	Maria Larsson	Åkergatan 24	Bräcke	S-844 67	Sweden
25	Frankenversand	Peter Franken	Berliner Platz 43	München	80805	Germany
26	France restauration	Carine Schmitt	54, rue Royale	Nantes	44000	France
27	Franchi S.p.A.	Paolo Accorti	Via Monte Bianco 34	Torino	10100	Italy
28	Furia Bacalhau e Frutos do Mar	Lino Rodriguez	Jardim das rosas n. 32	Lisboa	1675	Portugal
29	Galería del gastrónomo	Eduardo Saavedra	Rambla de Cataluña, 23	Barcelona	08022	Spain
30	Godos Cocina Típica	José Pedro Freyre	C/ Romero, 33	Sevilla	41101	Spain
31	Gourmet Lanchonetes	André Fonseca	Av. Brasil, 442	Campinas	04876-786	Brazil
32	Great Lakes Food Market	Howard Snyder	2732 Baker Blvd.	Eugene	97403	USA
33	GROSELLA-Restaurante	Manuel Pereira	5ª Ave. Los Palos Grandes	Caracas	1081	Venezuela
34	Hanari Carnes	Mario Pontes	Rua do Paço, 67	Rio de Janeiro	05454-876	Brazil
35	HILARIÓN-Abastos	Carlos Hernández	Carrera 22 con Ave. Carlos Soublette #8-35	San Cristóbal	5022	Venezuela
36	Hungry Coyote Import Store	Yoshi Latimer	City Center Plaza 516 Main St.	Elgin	97827	USA
37	Hungry Owl All-Night Grocers	Patricia McKenna	8 Johnstown Road	Cork		Ireland
38	Island Trading	Helen Bennett	Garden House Crowther Way	Cowes	PO31 7PJ	UK
39	Königlich Essen	Philip Cramer	Maubelstr. 90	Brandenburg	14776	Germany
40	La corne d'abondance	Daniel Tonini	67, avenue de l'Europe	Versailles	78000	France
41	La maison d'Asie	Annette Roulet	1 rue Alsace-Lorraine	Toulouse	31000	France
42	Laughing Bacchus Wine Cellars	Yoshi Tannamuri	1900 Oak St.	Vancouver	V3F 2K1	Canada
43	Lazy K Kountry Store	John Steel	12 Orchestra Terrace	Walla Walla	99362	USA
44	Lehmanns Marktstand	Renate Messner	Magazinweg 7	Frankfurt a.M.	60528	Germany
45	Let's Stop N Shop	Jaime Yorres	87 Polk St. Suite 5	San Francisco	94117	USA
46	LILA-Supermercado	Carlos González	Carrera 52 con Ave. Bolívar #65-98 Llano Largo	Barquisimeto	3508	Venezuela
47	LINO-Delicateses	Felipe Izquierdo	Ave. 5 de Mayo Porlamar	I. de Margarita	4980	Venezuela
48	Lonesome Pine Restaurant	Fran Wilson	89 Chiaroscuro Rd.	Portland	97219	USA
49	Magazzini Alimentari Riuniti	Giovanni Rovelli	Via Ludovico il Moro 22	Bergamo	24100	Italy
50	Maison Dewey	Catherine Dewey	Rue Joseph-Bens 532	Bruxelles	B-1180	Belgium
51	Mère Paillarde	Jean Fresnière	43 rue St. Laurent	Montréal	H1J 1C3	Canada
52	Morgenstern Gesundkost	Alexander Feuer	Heerstr. 22	Leipzig	04179	Germany
53	North/South	Simon Crowther	South House 300 Queensbridge	London	SW7 1RZ	UK
54	Océano Atlántico Ltda.	Yvonne Moncada	Ing. Gustavo Moncada 8585 Piso 20-A	Buenos Aires	1010	Argentina
55	Old World Delicatessen	Rene Phillips	2743 Bering St.	Anchorage	99508	USA
56	Ottilies Käseladen	Henriette Pfalzheim	Mehrheimerstr. 369	Köln	50739	Germany
57	Paris spécialités	Marie Bertrand	265, boulevard Charonne	Paris	75012	France
58	Pericles Comidas clásicas	Guillermo Fernández	Calle Dr. Jorge Cash 321	México D.F.	05033	Mexico
59	Piccolo und mehr	Georg Pipps	Geislweg 14	Salzburg	5020	Austria
60	Princesa Isabel Vinhoss	Isabel de Castro	Estrada da saúde n. 58	Lisboa	1756	Portugal
61	Que Delícia	Bernardo Batista	Rua da Panificadora, 12	Rio de Janeiro	02389-673	Brazil
62	Queen Cozinha	Lúcia Carvalho	Alameda dos Canàrios, 891	São Paulo	05487-020	Brazil
63	QUICK-Stop	Horst Kloss	Taucherstraße 10	Cunewalde	01307	Germany
64	Rancho grande	Sergio Gutiérrez	Av. del Libertador 900	Buenos Aires	1010	Argentina
65	Rattlesnake Canyon Grocery	Paula Wilson	2817 Milton Dr.	Albuquerque	87110	USA
66	Reggiani Caseifici	Maurizio Moroni	Strada Provinciale 124	Reggio Emilia	42100	Italy
67	Ricardo Adocicados	Janete Limeira	Av. Copacabana, 267	Rio de Janeiro	02389-890	Brazil
68	Richter Supermarkt	Michael Holz	Grenzacherweg 237	Genève	1203	Switzerland
69	Romero y tomillo	Alejandra Camino	Gran Vía, 1	Madrid	28001	Spain
70	Santé Gourmet	Jonas Bergulfsen	Erling Skakkes gate 78	Stavern	4110	Norway
71	Save-a-lot Markets	Jose Pavarotti	187 Suffolk Ln.	Boise	83720	USA
72	Seven Seas Imports	Hari Kumar	90 Wadhurst Rd.	London	OX15 4NB	UK
73	Simons bistro	Jytte Petersen	Vinbæltet 34	København	1734	Denmark
74	Spécialités du monde	Dominique Perrier	25, rue Lauriston	Paris	75016	France
75	Split Rail Beer & Ale	Art Braunschweiger	P.O. Box 555	Lander	82520	USA
76	Suprêmes délices	Pascale Cartrain	Boulevard Tirou, 255	Charleroi	B-6000	Belgium
77	The Big Cheese	Liz Nixon	89 Jefferson Way Suite 2	Portland	97201	USA
78	The Cracker Box	Liu Wong	55 Grizzly Peak Rd.	Butte	59801	USA
79	Toms Spezialitäten	Karin Josephs	Luisenstr. 48	Münster	44087	Germany
80	Tortuga Restaurante	Miguel Angel Paolino	Avda. Azteca 123	México D.F.	05033	Mexico
81	Tradição Hipermercados	Anabela Domingues	Av. Inês de Castro, 414	São Paulo	05634-030	Brazil
82	Trail's Head Gourmet Provisioners	Helvetius Nagy	722 DaVinci Blvd.	Kirkland	98034	USA
83	Vaffeljernet	Palle Ibsen	Smagsløget 45	Århus	8200	Denmark
84	Victuailles en stock	Mary Saveley	2, rue du Commerce	Lyon	69004	France
85	Vins et alcools Chevalier	Paul Henriot	59 rue de l'Abbaye	Reims	51100	France
86	Die Wandernde Kuh	Rita Müller	Adenauerallee 900	Stuttgart	70563	Germany
87	Wartian Herkku	Pirkko Koskitalo	Torikatu 38	Oulu	90110	Finland
88	Wellington Importadora	Paula Parente	Rua do Mercado, 12	Resende	08737-363	Brazil
89	White Clover Markets	Karl Jablonski	305 - 14th Ave. S. Suite 3B	Seattle	98128	USA
90	Wilman Kala	Matti Karttunen	Keskuskatu 45	Helsinki	21240	Finland
91	Wolski	Zbyszek	ul. Filtrowa 68	Walla	01-012	Poland

All Conditions Must Be True

The following SQL statement selects all fields from Customers where Country is "Germany" AND City is "Berlin" AND PostalCode is higher than 12000:

Example

SELECT * FROM Customers
WHERE Country = 'Germany'
AND City = 'Berlin'
AND PostalCode > 1200;

Combining AND and OR

You can combine the AND and OR operators.

The following SQL statement selects all customers from Spain that starts with a "G" or an "R".

Make sure you use parenthesis to get the correct result.

Example

Select all Spanish customers that starts with either "G" or "R":

SELECT * FROM Customers
WHERE Country = 'Spain' AND (CustomerName LIKE 'G%' OR CustomerName LIKE 'R%');

Without parenthesis, the select statement will return all customers from Spain that starts with a "G", plus all customers that starts with an "R", regardless of the country value:

Example

Select all customers that either:
are from Spain and starts with either "G", or
starts with the letter "R":

SELECT * FROM Customers
WHERE Country = 'Spain' AND CustomerName LIKE 'G%' OR CustomerName LIKE 'R%';

The SQL OR Operator

The WHERE clause can contain one or more OR operators.

The OR operator is used to filter records based on more than one condition, like if you want to return all customers from Germany but also those from Spain:

Example

Select all customers from Germany or Spain:

SELECT *
FROM Customers
WHERE Country = 'Germany' OR Country = 'Spain';

Syntax

SELECT column1, column2, ...
FROM table_name
WHERE condition1 OR condition2 OR condition3 ...;

OR vs AND

The OR operator displays a record if any of the conditions are TRUE.

The AND operator displays a record if all the conditions are TRUE.

Demo Database

The table below shows the complete "Customers" table from the Northwind sample database:

CustomerID	CustomerName	ContactName	Address	City	PostalCode	Country
1	Alfreds Futterkiste	Maria Anders	Obere Str. 57	Berlin	12209	Germany
2	Ana Trujillo Emparedados y helados	Ana Trujillo	Avda. de la Constitución 2222	México D.F.	05021	Mexico
3	Antonio Moreno Taquería	Antonio Moreno	Mataderos 2312	México D.F.	05023	Mexico
4	Around the Horn	Thomas Hardy	120 Hanover Sq.	London	WA1 1DP	UK
5	Berglunds snabbköp	Christina Berglund	Berguvsvägen 8	Luleå	S-958 22	Sweden
6	Blauer See Delikatessen	Hanna Moos	Forsterstr. 57	Mannheim	68306	Germany
7	Blondel père et fils	Frédérique Citeaux	24, place Kléber	Strasbourg	67000	France
8	Bólido Comidas preparadas	Martín Sommer	C/ Araquil, 67	Madrid	28023	Spain
9	Bon app'	Laurence Lebihans	12, rue des Bouchers	Marseille	13008	France
10	Bottom-Dollar Marketse	Elizabeth Lincoln	23 Tsawassen Blvd.	Tsawassen	T2F 8M4	Canada
11	B's Beverages	Victoria Ashworth	Fauntleroy Circus	London	EC2 5NT	UK
12	Cactus Comidas para llevar	Patricio Simpson	Cerrito 333	Buenos Aires	1010	Argentina
13	Centro comercial Moctezuma	Francisco Chang	Sierras de Granada 9993	México D.F.	05022	Mexico
14	Chop-suey Chinese	Yang Wang	Hauptstr. 29	Bern	3012	Switzerland
15	Comércio Mineiro	Pedro Afonso	Av. dos Lusíadas, 23	São Paulo	05432-043	Brazil
16	Consolidated Holdings	Elizabeth Brown	Berkeley Gardens 12 Brewery	London	WX1 6LT	UK
17	Drachenblut Delikatessend	Sven Ottlieb	Walserweg 21	Aachen	52066	Germany
18	Du monde entier	Janine Labrune	67, rue des Cinquante Otages	Nantes	44000	France
19	Eastern Connection	Ann Devon	35 King George	London	WX3 6FW	UK
20	Ernst Handel	Roland Mendel	Kirchgasse 6	Graz	8010	Austria
21	Familia Arquibaldo	Aria Cruz	Rua Orós, 92	São Paulo	05442-030	Brazil
22	FISSA Fabrica Inter. Salchichas S.A.	Diego Roel	C/ Moralzarzal, 86	Madrid	28034	Spain
23	Folies gourmandes	Martine Rancé	184, chaussée de Tournai	Lille	59000	France
24	Folk och fä HB	Maria Larsson	Åkergatan 24	Bräcke	S-844 67	Sweden
25	Frankenversand	Peter Franken	Berliner Platz 43	München	80805	Germany
26	France restauration	Carine Schmitt	54, rue Royale	Nantes	44000	France
27	Franchi S.p.A.	Paolo Accorti	Via Monte Bianco 34	Torino	10100	Italy
28	Furia Bacalhau e Frutos do Mar	Lino Rodriguez	Jardim das rosas n. 32	Lisboa	1675	Portugal
29	Galería del gastrónomo	Eduardo Saavedra	Rambla de Cataluña, 23	Barcelona	08022	Spain
30	Godos Cocina Típica	José Pedro Freyre	C/ Romero, 33	Sevilla	41101	Spain
31	Gourmet Lanchonetes	André Fonseca	Av. Brasil, 442	Campinas	04876-786	Brazil
32	Great Lakes Food Market	Howard Snyder	2732 Baker Blvd.	Eugene	97403	USA
33	GROSELLA-Restaurante	Manuel Pereira	5ª Ave. Los Palos Grandes	Caracas	1081	Venezuela
34	Hanari Carnes	Mario Pontes	Rua do Paço, 67	Rio de Janeiro	05454-876	Brazil
35	HILARIÓN-Abastos	Carlos Hernández	Carrera 22 con Ave. Carlos Soublette #8-35	San Cristóbal	5022	Venezuela
36	Hungry Coyote Import Store	Yoshi Latimer	City Center Plaza 516 Main St.	Elgin	97827	USA
37	Hungry Owl All-Night Grocers	Patricia McKenna	8 Johnstown Road	Cork		Ireland
38	Island Trading	Helen Bennett	Garden House Crowther Way	Cowes	PO31 7PJ	UK
39	Königlich Essen	Philip Cramer	Maubelstr. 90	Brandenburg	14776	Germany
40	La corne d'abondance	Daniel Tonini	67, avenue de l'Europe	Versailles	78000	France
41	La maison d'Asie	Annette Roulet	1 rue Alsace-Lorraine	Toulouse	31000	France
42	Laughing Bacchus Wine Cellars	Yoshi Tannamuri	1900 Oak St.	Vancouver	V3F 2K1	Canada
43	Lazy K Kountry Store	John Steel	12 Orchestra Terrace	Walla Walla	99362	USA
44	Lehmanns Marktstand	Renate Messner	Magazinweg 7	Frankfurt a.M.	60528	Germany
45	Let's Stop N Shop	Jaime Yorres	87 Polk St. Suite 5	San Francisco	94117	USA
46	LILA-Supermercado	Carlos González	Carrera 52 con Ave. Bolívar #65-98 Llano Largo	Barquisimeto	3508	Venezuela
47	LINO-Delicateses	Felipe Izquierdo	Ave. 5 de Mayo Porlamar	I. de Margarita	4980	Venezuela
48	Lonesome Pine Restaurant	Fran Wilson	89 Chiaroscuro Rd.	Portland	97219	USA
49	Magazzini Alimentari Riuniti	Giovanni Rovelli	Via Ludovico il Moro 22	Bergamo	24100	Italy
50	Maison Dewey	Catherine Dewey	Rue Joseph-Bens 532	Bruxelles	B-1180	Belgium
51	Mère Paillarde	Jean Fresnière	43 rue St. Laurent	Montréal	H1J 1C3	Canada
52	Morgenstern Gesundkost	Alexander Feuer	Heerstr. 22	Leipzig	04179	Germany
53	North/South	Simon Crowther	South House 300 Queensbridge	London	SW7 1RZ	UK
54	Océano Atlántico Ltda.	Yvonne Moncada	Ing. Gustavo Moncada 8585 Piso 20-A	Buenos Aires	1010	Argentina
55	Old World Delicatessen	Rene Phillips	2743 Bering St.	Anchorage	99508	USA
56	Ottilies Käseladen	Henriette Pfalzheim	Mehrheimerstr. 369	Köln	50739	Germany
57	Paris spécialités	Marie Bertrand	265, boulevard Charonne	Paris	75012	France
58	Pericles Comidas clásicas	Guillermo Fernández	Calle Dr. Jorge Cash 321	México D.F.	05033	Mexico
59	Piccolo und mehr	Georg Pipps	Geislweg 14	Salzburg	5020	Austria
60	Princesa Isabel Vinhoss	Isabel de Castro	Estrada da saúde n. 58	Lisboa	1756	Portugal
61	Que Delícia	Bernardo Batista	Rua da Panificadora, 12	Rio de Janeiro	02389-673	Brazil
62	Queen Cozinha	Lúcia Carvalho	Alameda dos Canàrios, 891	São Paulo	05487-020	Brazil
63	QUICK-Stop	Horst Kloss	Taucherstraße 10	Cunewalde	01307	Germany
64	Rancho grande	Sergio Gutiérrez	Av. del Libertador 900	Buenos Aires	1010	Argentina
65	Rattlesnake Canyon Grocery	Paula Wilson	2817 Milton Dr.	Albuquerque	87110	USA
66	Reggiani Caseifici	Maurizio Moroni	Strada Provinciale 124	Reggio Emilia	42100	Italy
67	Ricardo Adocicados	Janete Limeira	Av. Copacabana, 267	Rio de Janeiro	02389-890	Brazil
68	Richter Supermarkt	Michael Holz	Grenzacherweg 237	Genève	1203	Switzerland
69	Romero y tomillo	Alejandra Camino	Gran Vía, 1	Madrid	28001	Spain
70	Santé Gourmet	Jonas Bergulfsen	Erling Skakkes gate 78	Stavern	4110	Norway
71	Save-a-lot Markets	Jose Pavarotti	187 Suffolk Ln.	Boise	83720	USA
72	Seven Seas Imports	Hari Kumar	90 Wadhurst Rd.	London	OX15 4NB	UK
73	Simons bistro	Jytte Petersen	Vinbæltet 34	København	1734	Denmark
74	Spécialités du monde	Dominique Perrier	25, rue Lauriston	Paris	75016	France
75	Split Rail Beer & Ale	Art Braunschweiger	P.O. Box 555	Lander	82520	USA
76	Suprêmes délices	Pascale Cartrain	Boulevard Tirou, 255	Charleroi	B-6000	Belgium
77	The Big Cheese	Liz Nixon	89 Jefferson Way Suite 2	Portland	97201	USA
78	The Cracker Box	Liu Wong	55 Grizzly Peak Rd.	Butte	59801	USA
79	Toms Spezialitäten	Karin Josephs	Luisenstr. 48	Münster	44087	Germany
80	Tortuga Restaurante	Miguel Angel Paolino	Avda. Azteca 123	México D.F.	05033	Mexico
81	Tradição Hipermercados	Anabela Domingues	Av. Inês de Castro, 414	São Paulo	05634-030	Brazil
82	Trail's Head Gourmet Provisioners	Helvetius Nagy	722 DaVinci Blvd.	Kirkland	98034	USA
83	Vaffeljernet	Palle Ibsen	Smagsløget 45	Århus	8200	Denmark
84	Victuailles en stock	Mary Saveley	2, rue du Commerce	Lyon	69004	France
85	Vins et alcools Chevalier	Paul Henriot	59 rue de l'Abbaye	Reims	51100	France
86	Die Wandernde Kuh	Rita Müller	Adenauerallee 900	Stuttgart	70563	Germany
87	Wartian Herkku	Pirkko Koskitalo	Torikatu 38	Oulu	90110	Finland
88	Wellington Importadora	Paula Parente	Rua do Mercado, 12	Resende	08737-363	Brazil
89	White Clover Markets	Karl Jablonski	305 - 14th Ave. S. Suite 3B	Seattle	98128	USA
90	Wilman Kala	Matti Karttunen	Keskuskatu 45	Helsinki	21240	Finland
91	Wolski	Zbyszek	ul. Filtrowa 68	Walla	01-012	Poland

At Least One Condition Must Be True

The following SQL statement selects all fields from Customers where either City is "Berlin", CustomerName starts with the letter "G" or Country is "Norway":

Example

SELECT * FROM Customers
WHERE City = 'Berlin' OR CustomerName LIKE 'G%' OR Country = 'Norway';

Combining AND and OR

You can combine the AND and OR operators.

The following SQL statement selects all customers from Spain that starts with a "G" or an "R".

Make sure you use parenthesis to get the correct result.

Example

Select all Spanish customers that starts with either "G" or "R":

SELECT * FROM Customers
WHERE Country = 'Spain' AND (CustomerName LIKE 'G%' OR CustomerName LIKE 'R%');

Without parenthesis, the select statement will return all customers from Spain that starts with a "G", plus all customers that starts with an "R", regardless of the country value:

Example

Select all customers that either:
are from Spain and starts with either "G", or
starts with the letter "R":

SELECT * FROM Customers
WHERE Country = 'Spain' AND CustomerName LIKE 'G%' OR CustomerName LIKE 'R%';

The NOT Operator

The NOT operator is used in combination with other operators to give the opposite result, also called the negative result.

In the select statement below we want to return all customers that are NOT from Spain:

Example

Select only the customers that are NOT from Spain:

SELECT * FROM Customers
WHERE NOT Country = 'Spain';

In the example above, the NOT operator is used in combination with the = operator, but it can be used in combination with other comparison and/or logical operators. See examples below.

Syntax

SELECT column1, column2, ...
FROM table_name
WHERE NOT condition;

Demo Database

The table below shows the complete "Customers" table from the Northwind sample database:

CustomerID	CustomerName	ContactName	Address	City	PostalCode	Country
1	Alfreds Futterkiste	Maria Anders	Obere Str. 57	Berlin	12209	Germany
2	Ana Trujillo Emparedados y helados	Ana Trujillo	Avda. de la Constitución 2222	México D.F.	05021	Mexico
3	Antonio Moreno Taquería	Antonio Moreno	Mataderos 2312	México D.F.	05023	Mexico
4	Around the Horn	Thomas Hardy	120 Hanover Sq.	London	WA1 1DP	UK
5	Berglunds snabbköp	Christina Berglund	Berguvsvägen 8	Luleå	S-958 22	Sweden
6	Blauer See Delikatessen	Hanna Moos	Forsterstr. 57	Mannheim	68306	Germany
7	Blondel père et fils	Frédérique Citeaux	24, place Kléber	Strasbourg	67000	France
8	Bólido Comidas preparadas	Martín Sommer	C/ Araquil, 67	Madrid	28023	Spain
9	Bon app'	Laurence Lebihans	12, rue des Bouchers	Marseille	13008	France
10	Bottom-Dollar Marketse	Elizabeth Lincoln	23 Tsawassen Blvd.	Tsawassen	T2F 8M4	Canada
11	B's Beverages	Victoria Ashworth	Fauntleroy Circus	London	EC2 5NT	UK
12	Cactus Comidas para llevar	Patricio Simpson	Cerrito 333	Buenos Aires	1010	Argentina
13	Centro comercial Moctezuma	Francisco Chang	Sierras de Granada 9993	México D.F.	05022	Mexico
14	Chop-suey Chinese	Yang Wang	Hauptstr. 29	Bern	3012	Switzerland
15	Comércio Mineiro	Pedro Afonso	Av. dos Lusíadas, 23	São Paulo	05432-043	Brazil
16	Consolidated Holdings	Elizabeth Brown	Berkeley Gardens 12 Brewery	London	WX1 6LT	UK
17	Drachenblut Delikatessend	Sven Ottlieb	Walserweg 21	Aachen	52066	Germany
18	Du monde entier	Janine Labrune	67, rue des Cinquante Otages	Nantes	44000	France
19	Eastern Connection	Ann Devon	35 King George	London	WX3 6FW	UK
20	Ernst Handel	Roland Mendel	Kirchgasse 6	Graz	8010	Austria
21	Familia Arquibaldo	Aria Cruz	Rua Orós, 92	São Paulo	05442-030	Brazil
22	FISSA Fabrica Inter. Salchichas S.A.	Diego Roel	C/ Moralzarzal, 86	Madrid	28034	Spain
23	Folies gourmandes	Martine Rancé	184, chaussée de Tournai	Lille	59000	France
24	Folk och fä HB	Maria Larsson	Åkergatan 24	Bräcke	S-844 67	Sweden
25	Frankenversand	Peter Franken	Berliner Platz 43	München	80805	Germany
26	France restauration	Carine Schmitt	54, rue Royale	Nantes	44000	France
27	Franchi S.p.A.	Paolo Accorti	Via Monte Bianco 34	Torino	10100	Italy
28	Furia Bacalhau e Frutos do Mar	Lino Rodriguez	Jardim das rosas n. 32	Lisboa	1675	Portugal
29	Galería del gastrónomo	Eduardo Saavedra	Rambla de Cataluña, 23	Barcelona	08022	Spain
30	Godos Cocina Típica	José Pedro Freyre	C/ Romero, 33	Sevilla	41101	Spain
31	Gourmet Lanchonetes	André Fonseca	Av. Brasil, 442	Campinas	04876-786	Brazil
32	Great Lakes Food Market	Howard Snyder	2732 Baker Blvd.	Eugene	97403	USA
33	GROSELLA-Restaurante	Manuel Pereira	5ª Ave. Los Palos Grandes	Caracas	1081	Venezuela
34	Hanari Carnes	Mario Pontes	Rua do Paço, 67	Rio de Janeiro	05454-876	Brazil
35	HILARIÓN-Abastos	Carlos Hernández	Carrera 22 con Ave. Carlos Soublette #8-35	San Cristóbal	5022	Venezuela
36	Hungry Coyote Import Store	Yoshi Latimer	City Center Plaza 516 Main St.	Elgin	97827	USA
37	Hungry Owl All-Night Grocers	Patricia McKenna	8 Johnstown Road	Cork		Ireland
38	Island Trading	Helen Bennett	Garden House Crowther Way	Cowes	PO31 7PJ	UK
39	Königlich Essen	Philip Cramer	Maubelstr. 90	Brandenburg	14776	Germany
40	La corne d'abondance	Daniel Tonini	67, avenue de l'Europe	Versailles	78000	France
41	La maison d'Asie	Annette Roulet	1 rue Alsace-Lorraine	Toulouse	31000	France
42	Laughing Bacchus Wine Cellars	Yoshi Tannamuri	1900 Oak St.	Vancouver	V3F 2K1	Canada
43	Lazy K Kountry Store	John Steel	12 Orchestra Terrace	Walla Walla	99362	USA
44	Lehmanns Marktstand	Renate Messner	Magazinweg 7	Frankfurt a.M.	60528	Germany
45	Let's Stop N Shop	Jaime Yorres	87 Polk St. Suite 5	San Francisco	94117	USA
46	LILA-Supermercado	Carlos González	Carrera 52 con Ave. Bolívar #65-98 Llano Largo	Barquisimeto	3508	Venezuela
47	LINO-Delicateses	Felipe Izquierdo	Ave. 5 de Mayo Porlamar	I. de Margarita	4980	Venezuela
48	Lonesome Pine Restaurant	Fran Wilson	89 Chiaroscuro Rd.	Portland	97219	USA
49	Magazzini Alimentari Riuniti	Giovanni Rovelli	Via Ludovico il Moro 22	Bergamo	24100	Italy
50	Maison Dewey	Catherine Dewey	Rue Joseph-Bens 532	Bruxelles	B-1180	Belgium
51	Mère Paillarde	Jean Fresnière	43 rue St. Laurent	Montréal	H1J 1C3	Canada
52	Morgenstern Gesundkost	Alexander Feuer	Heerstr. 22	Leipzig	04179	Germany
53	North/South	Simon Crowther	South House 300 Queensbridge	London	SW7 1RZ	UK
54	Océano Atlántico Ltda.	Yvonne Moncada	Ing. Gustavo Moncada 8585 Piso 20-A	Buenos Aires	1010	Argentina
55	Old World Delicatessen	Rene Phillips	2743 Bering St.	Anchorage	99508	USA
56	Ottilies Käseladen	Henriette Pfalzheim	Mehrheimerstr. 369	Köln	50739	Germany
57	Paris spécialités	Marie Bertrand	265, boulevard Charonne	Paris	75012	France
58	Pericles Comidas clásicas	Guillermo Fernández	Calle Dr. Jorge Cash 321	México D.F.	05033	Mexico
59	Piccolo und mehr	Georg Pipps	Geislweg 14	Salzburg	5020	Austria
60	Princesa Isabel Vinhoss	Isabel de Castro	Estrada da saúde n. 58	Lisboa	1756	Portugal
61	Que Delícia	Bernardo Batista	Rua da Panificadora, 12	Rio de Janeiro	02389-673	Brazil
62	Queen Cozinha	Lúcia Carvalho	Alameda dos Canàrios, 891	São Paulo	05487-020	Brazil
63	QUICK-Stop	Horst Kloss	Taucherstraße 10	Cunewalde	01307	Germany
64	Rancho grande	Sergio Gutiérrez	Av. del Libertador 900	Buenos Aires	1010	Argentina
65	Rattlesnake Canyon Grocery	Paula Wilson	2817 Milton Dr.	Albuquerque	87110	USA
66	Reggiani Caseifici	Maurizio Moroni	Strada Provinciale 124	Reggio Emilia	42100	Italy
67	Ricardo Adocicados	Janete Limeira	Av. Copacabana, 267	Rio de Janeiro	02389-890	Brazil
68	Richter Supermarkt	Michael Holz	Grenzacherweg 237	Genève	1203	Switzerland
69	Romero y tomillo	Alejandra Camino	Gran Vía, 1	Madrid	28001	Spain
70	Santé Gourmet	Jonas Bergulfsen	Erling Skakkes gate 78	Stavern	4110	Norway
71	Save-a-lot Markets	Jose Pavarotti	187 Suffolk Ln.	Boise	83720	USA
72	Seven Seas Imports	Hari Kumar	90 Wadhurst Rd.	London	OX15 4NB	UK
73	Simons bistro	Jytte Petersen	Vinbæltet 34	København	1734	Denmark
74	Spécialités du monde	Dominique Perrier	25, rue Lauriston	Paris	75016	France
75	Split Rail Beer & Ale	Art Braunschweiger	P.O. Box 555	Lander	82520	USA
76	Suprêmes délices	Pascale Cartrain	Boulevard Tirou, 255	Charleroi	B-6000	Belgium
77	The Big Cheese	Liz Nixon	89 Jefferson Way Suite 2	Portland	97201	USA
78	The Cracker Box	Liu Wong	55 Grizzly Peak Rd.	Butte	59801	USA
79	Toms Spezialitäten	Karin Josephs	Luisenstr. 48	Münster	44087	Germany
80	Tortuga Restaurante	Miguel Angel Paolino	Avda. Azteca 123	México D.F.	05033	Mexico
81	Tradição Hipermercados	Anabela Domingues	Av. Inês de Castro, 414	São Paulo	05634-030	Brazil
82	Trail's Head Gourmet Provisioners	Helvetius Nagy	722 DaVinci Blvd.	Kirkland	98034	USA
83	Vaffeljernet	Palle Ibsen	Smagsløget 45	Århus	8200	Denmark
84	Victuailles en stock	Mary Saveley	2, rue du Commerce	Lyon	69004	France
85	Vins et alcools Chevalier	Paul Henriot	59 rue de l'Abbaye	Reims	51100	France
86	Die Wandernde Kuh	Rita Müller	Adenauerallee 900	Stuttgart	70563	Germany
87	Wartian Herkku	Pirkko Koskitalo	Torikatu 38	Oulu	90110	Finland
88	Wellington Importadora	Paula Parente	Rua do Mercado, 12	Resende	08737-363	Brazil
89	White Clover Markets	Karl Jablonski	305 - 14th Ave. S. Suite 3B	Seattle	98128	USA
90	Wilman Kala	Matti Karttunen	Keskuskatu 45	Helsinki	21240	Finland
91	Wolski	Zbyszek	ul. Filtrowa 68	Walla	01-012	Poland

NOT LIKE

Example

Select customers that does not start with the letter 'A':

SELECT * FROM Customers
WHERE CustomerName NOT LIKE 'A%';

NOT BETWEEN

Example

Select customers with a customerID not between 10 and 60:

SELECT * FROM Customers
WHERE CustomerID NOT BETWEEN 10 AND 60;

NOT IN

Example

Select customers that are not from Paris or London:

SELECT * FROM Customers
WHERE City NOT IN ('Paris', 'London');

NOT Greater Than

Example

Select customers with a CustomerId not greater than 50:

SELECT * FROM Customers
WHERE NOT CustomerID > 50;

Note: There is a not-greater-then operator: !> that would give you the same result.

NOT Less Than

Example

Select customers with a CustomerID not less than 50:

SELECT * FROM Customers
WHERE NOT CustomerId < 50;

Note: There is a not-less-then operator: !< that would give you the same result.

The SQL INSERT INTO Statement

The INSERT INTO statement is used to insert new records in a table.

INSERT INTO Syntax

It is possible to write the INSERT INTO statement in two ways:

1. Specify both the column names and the values to be inserted:

INSERT INTO table_name (column1, column2, column3, ...)
VALUES (value1, value2, value3, ...);

2. If you are adding values for all the columns of the table, you do not need to specify the column names in the SQL query. However, make sure the order of the values is in the same order as the columns in the table. Here, the INSERT INTO syntax would be as follows:

INSERT INTO table_name
VALUES (value1, value2, value3, ...);

Demo Database

Below is a selection from the "Customers" table in the Northwind sample database:

CustomerID	CustomerName	ContactName	Address	City	PostalCode	Country
89	White Clover Markets	Karl Jablonski	305 - 14th Ave. S. Suite 3B	Seattle	98128	USA
90	Wilman Kala	Matti Karttunen	Keskuskatu 45	Helsinki	21240	Finland
91	Wolski	Zbyszek	ul. Filtrowa 68	Walla	01-012	Poland

INSERT INTO Example

The following SQL statement inserts a new record in the "Customers" table:

Example

INSERT INTO Customers (CustomerName, ContactName, Address, City, PostalCode, Country)
VALUES ('Cardinal', 'Tom B. Erichsen', 'Skagen 21', 'Stavanger', '4006', 'Norway');

The selection from the "Customers" table will now look like this:

CustomerID	CustomerName	ContactName	Address	City	PostalCode	Country
89	White Clover Markets	Karl Jablonski	305 - 14th Ave. S. Suite 3B	Seattle	98128	USA
90	Wilman Kala	Matti Karttunen	Keskuskatu 45	Helsinki	21240	Finland
91	Wolski	Zbyszek	ul. Filtrowa 68	Walla	01-012	Poland
92	Cardinal	Tom B. Erichsen	Skagen 21	Stavanger	4006	Norway

Did you notice that we did not insert any number into the CustomerID field?
The CustomerID column is an field and will be generated automatically when a new record is inserted into the table.

Insert Data Only in Specified Columns

It is also possible to only insert data in specific columns.

The following SQL statement will insert a new record, but only insert data in the "CustomerName", "City", and "Country" columns (CustomerID will be updated automatically):

Example

INSERT INTO Customers (CustomerName, City, Country)
VALUES ('Cardinal', 'Stavanger', 'Norway');

The selection from the "Customers" table will now look like this:

CustomerID	CustomerName	ContactName	Address	City	PostalCode	Country
89	White Clover Markets	Karl Jablonski	305 - 14th Ave. S. Suite 3B	Seattle	98128	USA
90	Wilman Kala	Matti Karttunen	Keskuskatu 45	Helsinki	21240	Finland
91	Wolski	Zbyszek	ul. Filtrowa 68	Walla	01-012	Poland
92	Cardinal	null	null	Stavanger	null	Norway

Insert Multiple Rows

It is also possible to insert multiple rows in one statement.

To insert multiple rows of data, we use the same INSERT INTO statement, but with multiple values:

Example

INSERT INTO Customers (CustomerName, ContactName, Address, City, PostalCode, Country)
VALUES
('Cardinal', 'Tom B. Erichsen', 'Skagen 21', 'Stavanger', '4006', 'Norway'),
('Greasy Burger', 'Per Olsen', 'Gateveien 15', 'Sandnes', '4306', 'Norway'),
('Tasty Tee', 'Finn Egan', 'Streetroad 19B', 'Liverpool', 'L1 0AA', 'UK');

Make sure you separate each set of values with a comma ,.

The selection from the "Customers" table will now look like this:

CustomerID	CustomerName	ContactName	Address	City	PostalCode	Country
89	White Clover Markets	Karl Jablonski	305 - 14th Ave. S. Suite 3B	Seattle	98128	USA
90	Wilman Kala	Matti Karttunen	Keskuskatu 45	Helsinki	21240	Finland
91	Wolski	Zbyszek	ul. Filtrowa 68	Walla	01-012	Poland
92	Cardinal	Tom B. Erichsen	Skagen 21	Stavanger	4006	Norway
93	Greasy Burger	Per Olsen	Gateveien 15	Sandnes	4306	Norway
94	Tasty Tee	Finn Egan	Streetroad 19B	Liverpool	L1 0AA	UK

SQL NULL Values

What is a NULL Value?

A field with a NULL value is a field with no value.

If a field in a table is optional, it is possible to insert a new record or update a record without adding a value to this field. Then, the field will be saved with a NULL value.

Note: A NULL value is different from a zero value or a field that contains spaces. A field with a NULL value is one that has been left blank during record creation!

How to Test for NULL Values?

It is not possible to test for NULL values with comparison operators, such as =, <, or <>.

We will have to use the IS NULL and IS NOT NULL operators instead.

IS NULL Syntax

SELECT column_names
FROM table_name
WHERE column_name IS NULL;

IS NOT NULL Syntax

SELECT column_names
FROM table_name
WHERE column_name IS NOT NULL;

Demo Database

Below is a selection from the "Customers" table in the Northwind sample database:

CustomerID	CustomerName	ContactName	Address	City	PostalCode	Country
1	Alfreds Futterkiste	Maria Anders	Obere Str. 57	Berlin	12209	Germany
2	Ana Trujillo Emparedados y helados	Ana Trujillo	Avda. de la Constitución 2222	México D.F.	05021	Mexico
3	Antonio Moreno Taquería	Antonio Moreno	Mataderos 2312	México D.F.	05023	Mexico
4	Around the Horn	Thomas Hardy	120 Hanover Sq.	London	WA1 1DP	UK
5	Berglunds snabbköp	Christina Berglund	Berguvsvägen 8	Luleå	S-958 22	Sweden

The IS NULL Operator

The IS NULL operator is used to test for empty values (NULL values).

The following SQL lists all customers with a NULL value in the "Address" field:

Example

SELECT CustomerName, ContactName, Address
FROM Customers
WHERE Address IS NULL;

Tip: Always use IS NULL to look for NULL values.

The IS NOT NULL Operator

The IS NOT NULL operator is used to test for non-empty values (NOT NULL values).

The following SQL lists all customers with a value in the "Address" field:

Example

SELECT CustomerName, ContactName, Address
FROM Customers
WHERE Address IS NOT NULL;

The SQL UPDATE Statement

The UPDATE statement is used to modify the existing records in a table.

UPDATE Syntax

UPDATE table_name
SET column1 = value1, column2 = value2, ...
WHERE condition;

Note: Be careful when updating records in a table! Notice the WHERE clause in the UPDATE statement. The WHERE clause specifies which record(s) that should be updated. If you omit the WHERE clause, all records in the table will be updated!

Demo Database

Below is a selection from the "Customers" table in the Northwind sample database:

CustomerID	CustomerName	ContactName	Address	City	PostalCode	Country
1	Alfreds Futterkiste	Maria Anders	Obere Str. 57	Berlin	12209	Germany
2	Ana Trujillo Emparedados y helados	Ana Trujillo	Avda. de la Constitución 2222	México D.F.	05021	Mexico
3	Antonio Moreno Taquería	Antonio Moreno	Mataderos 2312	México D.F.	05023	Mexico
4	Around the Horn	Thomas Hardy	120 Hanover Sq.	London	WA1 1DP	UK
5	Berglunds snabbköp	Christina Berglund	Berguvsvägen 8	Luleå	S-958 22	Sweden

UPDATE Table

The following SQL statement updates the first customer (CustomerID = 1) with a new contact person and a new city.

Example

UPDATE Customers
SET ContactName = 'Alfred Schmidt', City= 'Frankfurt'
WHERE CustomerID = 1;

The selection from the "Customers" table will now look like this:

CustomerID	CustomerName	ContactName	Address	City	PostalCode	Country
1	Alfreds Futterkiste	Alfred Schmidt	Obere Str. 57	Frankfurt	12209	Germany
2	Ana Trujillo Emparedados y helados	Ana Trujillo	Avda. de la Constitución 2222	México D.F.	05021	Mexico
3	Antonio Moreno Taquería	Antonio Moreno	Mataderos 2312	México D.F.	05023	Mexico
4	Around the Horn	Thomas Hardy	120 Hanover Sq.	London	WA1 1DP	UK
5	Berglunds snabbköp	Christina Berglund	Berguvsvägen 8	Luleå	S-958 22	Sweden

UPDATE Multiple Records

It is the WHERE clause that determines how many records will be updated.

The following SQL statement will update the ContactName to "Juan" for all records where country is "Mexico":

Example

UPDATE Customers
SET ContactName='Juan'
WHERE Country='Mexico';

The selection from the "Customers" table will now look like this:

CustomerID	CustomerName	ContactName	Address	City	PostalCode	Country
1	Alfreds Futterkiste	Alfred Schmidt	Obere Str. 57	Frankfurt	12209	Germany
2	Ana Trujillo Emparedados y helados	Juan	Avda. de la Constitución 2222	México D.F.	05021	Mexico
3	Antonio Moreno Taquería	Juan	Mataderos 2312	México D.F.	05023	Mexico
4	Around the Horn	Thomas Hardy	120 Hanover Sq.	London	WA1 1DP	UK
5	Berglunds snabbköp	Christina Berglund	Berguvsvägen 8	Luleå	S-958 22	Sweden

Update Warning!

Be careful when updating records. If you omit the WHERE clause, ALL records will be updated!

Example

UPDATE Customers
SET ContactName='Juan';

The selection from the "Customers" table will now look like this:

CustomerID	CustomerName	ContactName	Address	City	PostalCode	Country
1	Alfreds Futterkiste	Juan	Obere Str. 57	Frankfurt	12209	Germany
2	Ana Trujillo Emparedados y helados	Juan	Avda. de la Constitución 2222	México D.F.	05021	Mexico
3	Antonio Moreno Taquería	Juan	Mataderos 2312	México D.F.	05023	Mexico
4	Around the Horn	Juan	120 Hanover Sq.	London	WA1 1DP	UK
5	Berglunds snabbköp	Juan	Berguvsvägen 8	Luleå	S-958 22	Sweden

The SQL DELETE Statement

The DELETE statement is used to delete existing records in a table.

DELETE Syntax

DELETE FROM table_name WHERE condition;

Note: Be careful when deleting records in a table! Notice the WHERE clause in the DELETE statement. The WHERE clause specifies which record(s) should be deleted. If you omit the WHERE clause, all records in the table will be deleted!

Demo Database

Below is a selection from the "Customers" table in the Northwind sample database:

CustomerID	CustomerName	ContactName	Address	City	PostalCode	Country
1	Alfreds Futterkiste	Maria Anders	Obere Str. 57	Berlin	12209	Germany
2	Ana Trujillo Emparedados y helados	Ana Trujillo	Avda. de la Constitución 2222	México D.F.	05021	Mexico
3	Antonio Moreno Taquería	Antonio Moreno	Mataderos 2312	México D.F.	05023	Mexico
4	Around the Horn	Thomas Hardy	120 Hanover Sq.	London	WA1 1DP	UK
5	Berglunds snabbköp	Christina Berglund	Berguvsvägen 8	Luleå	S-958 22	Sweden

SQL DELETE Example

The following SQL statement deletes the customer "Alfreds Futterkiste" from the "Customers" table:

Example

DELETE FROM Customers WHERE CustomerName='Alfreds Futterkiste';

The "Customers" table will now look like this:

CustomerID	CustomerName	ContactName	Address	City	PostalCode	Country
2	Ana Trujillo Emparedados y helados	Ana Trujillo	Avda. de la Constitución 2222	México D.F.	05021	Mexico
3	Antonio Moreno Taquería	Antonio Moreno	Mataderos 2312	México D.F.	05023	Mexico
4	Around the Horn	Thomas Hardy	120 Hanover Sq.	London	WA1 1DP	UK
5	Berglunds snabbköp	Christina Berglund	Berguvsvägen 8	Luleå	S-958 22	Sweden

Delete All Records

It is possible to delete all rows in a table without deleting the table. This means that the table structure, attributes, and indexes will be intact:

DELETE FROM table_name;

The following SQL statement deletes all rows in the "Customers" table, without deleting the table:

Example

DELETE FROM Customers;

Delete a Table

To delete the table completely, use the DROP TABLE statement:

Example

Remove the Customers table:

DROP TABLE Customers;

The SQL SELECT TOP Clause

The SELECT TOP clause is used to specify the number of records to return.

The SELECT TOP clause is useful on large tables with thousands of records. Returning a large number of records can impact performance.

Note: Not all database systems support the SELECT TOP clause. MySQL supports the LIMIT clause to select a limited number of records, while Oracle uses FETCH FIRST n ROWS ONLY and ROWNUM.

SQL Server / MS Access Syntax:

SELECT TOP number|percent column_name(s)
FROM table_name
WHERE condition;

MySQL Syntax:

SELECT column_name(s)
FROM table_name
WHERE condition
LIMIT number;

Oracle 12 Syntax:

SELECT column_name(s)
FROM table_name
ORDER BY column_name(s)
FETCH FIRST number ROWS ONLY;

Older Oracle Syntax:

SELECT column_name(s)
FROM table_name
WHERE ROWNUM <= number;

Older Oracle Syntax (with ORDER BY):

SELECT *
FROM (SELECT column_name(s) FROM table_name ORDER BY column_name(s))
WHERE ROWNUM <= number;

Demo Database

Below is a selection from the "Customers" table in the Northwind sample database:

CustomerID	CustomerName	ContactName	Address	City	PostalCode	Country
1	Alfreds Futterkiste	Maria Anders	Obere Str. 57	Berlin	12209	Germany
2	Ana Trujillo Emparedados y helados	Ana Trujillo	Avda. de la Constitución 2222	México D.F.	05021	Mexico
3	Antonio Moreno Taquería	Antonio Moreno	Mataderos 2312	México D.F.	05023	Mexico
4	Around the Horn	Thomas Hardy	120 Hanover Sq.	London	WA1 1DP	UK
5	Berglunds snabbköp	Christina Berglund	Berguvsvägen 8	Luleå	S-958 22	Sweden

SQL TOP, LIMIT and FETCH FIRST Examples

The following SQL statement selects the first three records from the "Customers" table (for SQL Server/MS Access):

Example

SELECT TOP 3 * FROM Customers;

The following SQL statement shows the equivalent example for MySQL:

Example

SELECT * FROM Customers
LIMIT 3;

The following SQL statement shows the equivalent example for Oracle:

Example

SELECT * FROM Customers
FETCH FIRST 3 ROWS ONLY;

SQL TOP PERCENT Example

The following SQL statement selects the first 50% of the records from the "Customers" table (for SQL Server/MS Access):

Example

SELECT TOP 50 PERCENT * FROM Customers;

The following SQL statement shows the equivalent example for Oracle:

Example

SELECT * FROM Customers
FETCH FIRST 50 PERCENT ROWS ONLY;

ADD a WHERE CLAUSE

The following SQL statement selects the first three records from the "Customers" table, where the country is "Germany" (for SQL Server/MS Access):

Example

SELECT TOP 3 * FROM Customers
WHERE Country='Germany';

The following SQL statement shows the equivalent example for MySQL:

Example

SELECT * FROM Customers
WHERE Country='Germany'
LIMIT 3;

The following SQL statement shows the equivalent example for Oracle:

Example

SELECT * FROM Customers
WHERE Country='Germany'
FETCH FIRST 3 ROWS ONLY;

The SQL MIN() and MAX() Functions

The MIN() function returns the smallest value of the selected column.

The MAX() function returns the largest value of the selected column.

MIN() Syntax

SELECT MIN(column_name)
FROM table_name
WHERE condition;

MAX() Syntax

SELECT MAX(column_name)
FROM table_name
WHERE condition;

Demo Database

Below is a selection from the "Products" table in the Northwind sample database:

ProductID	ProductName	SupplierID	CategoryID	Unit	Price
1	Chais	1	1	10 boxes x 20 bags	18
2	Chang	1	1	24 - 12 oz bottles	19
3	Aniseed Syrup	1	2	12 - 550 ml bottles	10
4	Chef Anton's Cajun Seasoning	2	2	48 - 6 oz jars	22
5	Chef Anton's Gumbo Mix	2	2	36 boxes	21.35

MIN() Example

The following SQL statement finds the price of the cheapest product:

Example

SELECT MIN(Price) AS SmallestPrice
FROM Products;

MAX() Example

The following SQL statement finds the price of the most expensive product:

Example

SELECT MAX(Price) AS LargestPrice
FROM Products;

The SQL COUNT(), AVG() and SUM() Functions

The COUNT() function returns the number of rows that matches a specified criterion.

COUNT() Syntax

SELECT COUNT(column_name)
FROM table_name
WHERE condition;

The AVG() function returns the average value of a numeric column.

AVG() Syntax

SELECT AVG(column_name)
FROM table_name
WHERE condition;

The SUM() function returns the total sum of a numeric column.

SUM() Syntax

SELECT SUM(column_name)
FROM table_name
WHERE condition;

Demo Database

Below is a selection from the "Products" table in the Northwind sample database:

ProductID	ProductName	SupplierID	CategoryID	Unit	Price
1	Chais	1	1	10 boxes x 20 bags	18
2	Chang	1	1	24 - 12 oz bottles	19
3	Aniseed Syrup	1	2	12 - 550 ml bottles	10
4	Chef Anton's Cajun Seasoning	2	2	48 - 6 oz jars	22
5	Chef Anton's Gumbo Mix	2	2	36 boxes	21.35

COUNT() Example

The following SQL statement finds the number of products:

Example

SELECT COUNT(ProductID)
FROM Products;

Note: NULL values are not counted.

AVG() Example

The following SQL statement finds the average price of all products:

Example

SELECT AVG(Price)
FROM Products;

Note: NULL values are ignored.

Demo Database

Below is a selection from the "OrderDetails" table in the Northwind sample database:

OrderDetailID	OrderID	ProductID	Quantity
1	10248	11	12
2	10248	42	10
3	10248	72	5
4	10249	14	9
5	10249	51	40

SUM() Example

The following SQL statement finds the sum of the "Quantity" fields in the "OrderDetails" table:

Example

SELECT SUM(Quantity)
FROM OrderDetails;

Note: NULL values are ignored.

The SQL LIKE Operator

The LIKE operator is used in a WHERE clause to search for a specified pattern in a column.

There are two wildcards often used in conjunction with the LIKE operator:

The percent sign (%) represents zero, one, or multiple characters
The underscore sign (_) represents one, single character

Note: MS Access uses an asterisk (*) instead of the percent sign (%), and a question mark (?) instead of the underscore (_).

The percent sign and the underscore can also be used in combinations!

LIKE Syntax

SELECT column1, column2, ...
FROM table_name
WHERE columnN LIKE pattern;

Tip: You can also combine any number of conditions using AND or OR operators.

Here are some examples showing different LIKE operators with '%' and '_' wildcards:

LIKE Operator	Description
WHERE CustomerName LIKE 'a%'	Finds any values that start with "a"
WHERE CustomerName LIKE '%a'	Finds any values that end with "a"
WHERE CustomerName LIKE '%or%'	Finds any values that have "or" in any position
WHERE CustomerName LIKE '_r%'	Finds any values that have "r" in the second position
WHERE CustomerName LIKE 'a_%'	Finds any values that start with "a" and are at least 2 characters in length
WHERE CustomerName LIKE 'a__%'	Finds any values that start with "a" and are at least 3 characters in length
WHERE ContactName LIKE 'a%o'	Finds any values that start with "a" and ends with "o"

Demo Database

The table below shows the complete "Customers" table from the Northwind sample database:

CustomerID	CustomerName	ContactName	Address	City	PostalCode	Country
1	Alfreds Futterkiste	Maria Anders	Obere Str. 57	Berlin	12209	Germany
2	Ana Trujillo Emparedados y helados	Ana Trujillo	Avda. de la Constitución 2222	México D.F.	05021	Mexico
3	Antonio Moreno Taquería	Antonio Moreno	Mataderos 2312	México D.F.	05023	Mexico
4	Around the Horn	Thomas Hardy	120 Hanover Sq.	London	WA1 1DP	UK
5	Berglunds snabbköp	Christina Berglund	Berguvsvägen 8	Luleå	S-958 22	Sweden
6	Blauer See Delikatessen	Hanna Moos	Forsterstr. 57	Mannheim	68306	Germany
7	Blondel père et fils	Frédérique Citeaux	24, place Kléber	Strasbourg	67000	France
8	Bólido Comidas preparadas	Martín Sommer	C/ Araquil, 67	Madrid	28023	Spain
9	Bon app'	Laurence Lebihans	12, rue des Bouchers	Marseille	13008	France
10	Bottom-Dollar Marketse	Elizabeth Lincoln	23 Tsawassen Blvd.	Tsawassen	T2F 8M4	Canada
11	B's Beverages	Victoria Ashworth	Fauntleroy Circus	London	EC2 5NT	UK
12	Cactus Comidas para llevar	Patricio Simpson	Cerrito 333	Buenos Aires	1010	Argentina
13	Centro comercial Moctezuma	Francisco Chang	Sierras de Granada 9993	México D.F.	05022	Mexico
14	Chop-suey Chinese	Yang Wang	Hauptstr. 29	Bern	3012	Switzerland
15	Comércio Mineiro	Pedro Afonso	Av. dos Lusíadas, 23	São Paulo	05432-043	Brazil
16	Consolidated Holdings	Elizabeth Brown	Berkeley Gardens 12 Brewery	London	WX1 6LT	UK
17	Drachenblut Delikatessend	Sven Ottlieb	Walserweg 21	Aachen	52066	Germany
18	Du monde entier	Janine Labrune	67, rue des Cinquante Otages	Nantes	44000	France
19	Eastern Connection	Ann Devon	35 King George	London	WX3 6FW	UK
20	Ernst Handel	Roland Mendel	Kirchgasse 6	Graz	8010	Austria
21	Familia Arquibaldo	Aria Cruz	Rua Orós, 92	São Paulo	05442-030	Brazil
22	FISSA Fabrica Inter. Salchichas S.A.	Diego Roel	C/ Moralzarzal, 86	Madrid	28034	Spain
23	Folies gourmandes	Martine Rancé	184, chaussée de Tournai	Lille	59000	France
24	Folk och fä HB	Maria Larsson	Åkergatan 24	Bräcke	S-844 67	Sweden
25	Frankenversand	Peter Franken	Berliner Platz 43	München	80805	Germany
26	France restauration	Carine Schmitt	54, rue Royale	Nantes	44000	France
27	Franchi S.p.A.	Paolo Accorti	Via Monte Bianco 34	Torino	10100	Italy
28	Furia Bacalhau e Frutos do Mar	Lino Rodriguez	Jardim das rosas n. 32	Lisboa	1675	Portugal
29	Galería del gastrónomo	Eduardo Saavedra	Rambla de Cataluña, 23	Barcelona	08022	Spain
30	Godos Cocina Típica	José Pedro Freyre	C/ Romero, 33	Sevilla	41101	Spain
31	Gourmet Lanchonetes	André Fonseca	Av. Brasil, 442	Campinas	04876-786	Brazil
32	Great Lakes Food Market	Howard Snyder	2732 Baker Blvd.	Eugene	97403	USA
33	GROSELLA-Restaurante	Manuel Pereira	5ª Ave. Los Palos Grandes	Caracas	1081	Venezuela
34	Hanari Carnes	Mario Pontes	Rua do Paço, 67	Rio de Janeiro	05454-876	Brazil
35	HILARIÓN-Abastos	Carlos Hernández	Carrera 22 con Ave. Carlos Soublette #8-35	San Cristóbal	5022	Venezuela
36	Hungry Coyote Import Store	Yoshi Latimer	City Center Plaza 516 Main St.	Elgin	97827	USA
37	Hungry Owl All-Night Grocers	Patricia McKenna	8 Johnstown Road	Cork		Ireland
38	Island Trading	Helen Bennett	Garden House Crowther Way	Cowes	PO31 7PJ	UK
39	Königlich Essen	Philip Cramer	Maubelstr. 90	Brandenburg	14776	Germany
40	La corne d'abondance	Daniel Tonini	67, avenue de l'Europe	Versailles	78000	France
41	La maison d'Asie	Annette Roulet	1 rue Alsace-Lorraine	Toulouse	31000	France
42	Laughing Bacchus Wine Cellars	Yoshi Tannamuri	1900 Oak St.	Vancouver	V3F 2K1	Canada
43	Lazy K Kountry Store	John Steel	12 Orchestra Terrace	Walla Walla	99362	USA
44	Lehmanns Marktstand	Renate Messner	Magazinweg 7	Frankfurt a.M.	60528	Germany
45	Let's Stop N Shop	Jaime Yorres	87 Polk St. Suite 5	San Francisco	94117	USA
46	LILA-Supermercado	Carlos González	Carrera 52 con Ave. Bolívar #65-98 Llano Largo	Barquisimeto	3508	Venezuela
47	LINO-Delicateses	Felipe Izquierdo	Ave. 5 de Mayo Porlamar	I. de Margarita	4980	Venezuela
48	Lonesome Pine Restaurant	Fran Wilson	89 Chiaroscuro Rd.	Portland	97219	USA
49	Magazzini Alimentari Riuniti	Giovanni Rovelli	Via Ludovico il Moro 22	Bergamo	24100	Italy
50	Maison Dewey	Catherine Dewey	Rue Joseph-Bens 532	Bruxelles	B-1180	Belgium
51	Mère Paillarde	Jean Fresnière	43 rue St. Laurent	Montréal	H1J 1C3	Canada
52	Morgenstern Gesundkost	Alexander Feuer	Heerstr. 22	Leipzig	04179	Germany
53	North/South	Simon Crowther	South House 300 Queensbridge	London	SW7 1RZ	UK
54	Océano Atlántico Ltda.	Yvonne Moncada	Ing. Gustavo Moncada 8585 Piso 20-A	Buenos Aires	1010	Argentina
55	Old World Delicatessen	Rene Phillips	2743 Bering St.	Anchorage	99508	USA
56	Ottilies Käseladen	Henriette Pfalzheim	Mehrheimerstr. 369	Köln	50739	Germany
57	Paris spécialités	Marie Bertrand	265, boulevard Charonne	Paris	75012	France
58	Pericles Comidas clásicas	Guillermo Fernández	Calle Dr. Jorge Cash 321	México D.F.	05033	Mexico
59	Piccolo und mehr	Georg Pipps	Geislweg 14	Salzburg	5020	Austria
60	Princesa Isabel Vinhoss	Isabel de Castro	Estrada da saúde n. 58	Lisboa	1756	Portugal
61	Que Delícia	Bernardo Batista	Rua da Panificadora, 12	Rio de Janeiro	02389-673	Brazil
62	Queen Cozinha	Lúcia Carvalho	Alameda dos Canàrios, 891	São Paulo	05487-020	Brazil
63	QUICK-Stop	Horst Kloss	Taucherstraße 10	Cunewalde	01307	Germany
64	Rancho grande	Sergio Gutiérrez	Av. del Libertador 900	Buenos Aires	1010	Argentina
65	Rattlesnake Canyon Grocery	Paula Wilson	2817 Milton Dr.	Albuquerque	87110	USA
66	Reggiani Caseifici	Maurizio Moroni	Strada Provinciale 124	Reggio Emilia	42100	Italy
67	Ricardo Adocicados	Janete Limeira	Av. Copacabana, 267	Rio de Janeiro	02389-890	Brazil
68	Richter Supermarkt	Michael Holz	Grenzacherweg 237	Genève	1203	Switzerland
69	Romero y tomillo	Alejandra Camino	Gran Vía, 1	Madrid	28001	Spain
70	Santé Gourmet	Jonas Bergulfsen	Erling Skakkes gate 78	Stavern	4110	Norway
71	Save-a-lot Markets	Jose Pavarotti	187 Suffolk Ln.	Boise	83720	USA
72	Seven Seas Imports	Hari Kumar	90 Wadhurst Rd.	London	OX15 4NB	UK
73	Simons bistro	Jytte Petersen	Vinbæltet 34	København	1734	Denmark
74	Spécialités du monde	Dominique Perrier	25, rue Lauriston	Paris	75016	France
75	Split Rail Beer & Ale	Art Braunschweiger	P.O. Box 555	Lander	82520	USA
76	Suprêmes délices	Pascale Cartrain	Boulevard Tirou, 255	Charleroi	B-6000	Belgium
77	The Big Cheese	Liz Nixon	89 Jefferson Way Suite 2	Portland	97201	USA
78	The Cracker Box	Liu Wong	55 Grizzly Peak Rd.	Butte	59801	USA
79	Toms Spezialitäten	Karin Josephs	Luisenstr. 48	Münster	44087	Germany
80	Tortuga Restaurante	Miguel Angel Paolino	Avda. Azteca 123	México D.F.	05033	Mexico
81	Tradição Hipermercados	Anabela Domingues	Av. Inês de Castro, 414	São Paulo	05634-030	Brazil
82	Trail's Head Gourmet Provisioners	Helvetius Nagy	722 DaVinci Blvd.	Kirkland	98034	USA
83	Vaffeljernet	Palle Ibsen	Smagsløget 45	Århus	8200	Denmark
84	Victuailles en stock	Mary Saveley	2, rue du Commerce	Lyon	69004	France
85	Vins et alcools Chevalier	Paul Henriot	59 rue de l'Abbaye	Reims	51100	France
86	Die Wandernde Kuh	Rita Müller	Adenauerallee 900	Stuttgart	70563	Germany
87	Wartian Herkku	Pirkko Koskitalo	Torikatu 38	Oulu	90110	Finland
88	Wellington Importadora	Paula Parente	Rua do Mercado, 12	Resende	08737-363	Brazil
89	White Clover Markets	Karl Jablonski	305 - 14th Ave. S. Suite 3B	Seattle	98128	USA
90	Wilman Kala	Matti Karttunen	Keskuskatu 45	Helsinki	21240	Finland
91	Wolski	Zbyszek	ul. Filtrowa 68	Walla	01-012	Poland

SQL LIKE Examples

The following SQL statement selects all customers with a CustomerName starting with "a":

Example

SELECT * FROM Customers
WHERE CustomerName LIKE 'a%';

The following SQL statement selects all customers with a CustomerName ending with "a":

Example

SELECT * FROM Customers
WHERE CustomerName LIKE '%a';

The following SQL statement selects all customers with a CustomerName that have "or" in any position:

Example

SELECT * FROM Customers
WHERE CustomerName LIKE '%or%';

The following SQL statement selects all customers with a CustomerName that have "r" in the second position:

Example

SELECT * FROM Customers
WHERE CustomerName LIKE '_r%';

The following SQL statement selects all customers with a CustomerName that starts with "a" and are at least 3 characters in length:

Example

SELECT * FROM Customers
WHERE CustomerName LIKE 'a__%';

The following SQL statement selects all customers with a ContactName that starts with "a" and ends with "o":

Example

SELECT * FROM Customers
WHERE ContactName LIKE 'a%o';

The following SQL statement selects all customers with a CustomerName that does NOT start with "a":

Example

SELECT * FROM Customers
WHERE CustomerName NOT LIKE 'a%';

SQL Wildcards

SQL Wildcard Characters

A wildcard character is used to substitute one or more characters in a string.

Wildcard characters are used with the operator. The LIKE operator is used in a WHERE clause to search for a specified pattern in a column.

Wildcard Characters in MS Access

Symbol	Description	Example
*	Represents zero or more characters	bl* finds bl, black, blue, and blob
?	Represents a single character	h?t finds hot, hat, and hit
[]	Represents any single character within the brackets	h[oa]t finds hot and hat, but not hit
!	Represents any character not in the brackets	h[!oa]t finds hit, but not hot and hat
-	Represents any single character within the specified range	c[a-b]t finds cat and cbt
#	Represents any single numeric character	2#5 finds 205, 215, 225, 235, 245, 255, 265, 275, 285, and 295

Wildcard Characters in SQL Server

Symbol	Description	Example
%	Represents zero or more characters	bl% finds bl, black, blue, and blob
_	Represents a single character	h_t finds hot, hat, and hit
[]	Represents any single character within the brackets	h[oa]t finds hot and hat, but not hit
^	Represents any character not in the brackets	h[^oa]t finds hit, but not hot and hat
-	Represents any single character within the specified range	c[a-b]t finds cat and cbt

All the wildcards can also be used in combinations!

Here are some examples showing different LIKE operators with '%' and '_' wildcards:

LIKE Operator	Description
WHERE CustomerName LIKE 'a%'	Finds any values that starts with "a"
WHERE CustomerName LIKE '%a'	Finds any values that ends with "a"
WHERE CustomerName LIKE '%or%'	Finds any values that have "or" in any position
WHERE CustomerName LIKE '_r%'	Finds any values that have "r" in the second position
WHERE CustomerName LIKE 'a__%'	Finds any values that starts with "a" and are at least 3 characters in length
WHERE ContactName LIKE 'a%o'	Finds any values that starts with "a" and ends with "o"

Demo Database

The table below shows the complete "Customers" table from the Northwind sample database:

CustomerID	CustomerName	ContactName	Address	City	PostalCode	Country
1	Alfreds Futterkiste	Maria Anders	Obere Str. 57	Berlin	12209	Germany
2	Ana Trujillo Emparedados y helados	Ana Trujillo	Avda. de la Constitución 2222	México D.F.	05021	Mexico
3	Antonio Moreno Taquería	Antonio Moreno	Mataderos 2312	México D.F.	05023	Mexico
4	Around the Horn	Thomas Hardy	120 Hanover Sq.	London	WA1 1DP	UK
5	Berglunds snabbköp	Christina Berglund	Berguvsvägen 8	Luleå	S-958 22	Sweden
6	Blauer See Delikatessen	Hanna Moos	Forsterstr. 57	Mannheim	68306	Germany
7	Blondel père et fils	Frédérique Citeaux	24, place Kléber	Strasbourg	67000	France
8	Bólido Comidas preparadas	Martín Sommer	C/ Araquil, 67	Madrid	28023	Spain
9	Bon app'	Laurence Lebihans	12, rue des Bouchers	Marseille	13008	France
10	Bottom-Dollar Marketse	Elizabeth Lincoln	23 Tsawassen Blvd.	Tsawassen	T2F 8M4	Canada
11	B's Beverages	Victoria Ashworth	Fauntleroy Circus	London	EC2 5NT	UK
12	Cactus Comidas para llevar	Patricio Simpson	Cerrito 333	Buenos Aires	1010	Argentina
13	Centro comercial Moctezuma	Francisco Chang	Sierras de Granada 9993	México D.F.	05022	Mexico
14	Chop-suey Chinese	Yang Wang	Hauptstr. 29	Bern	3012	Switzerland
15	Comércio Mineiro	Pedro Afonso	Av. dos Lusíadas, 23	São Paulo	05432-043	Brazil
16	Consolidated Holdings	Elizabeth Brown	Berkeley Gardens 12 Brewery	London	WX1 6LT	UK
17	Drachenblut Delikatessend	Sven Ottlieb	Walserweg 21	Aachen	52066	Germany
18	Du monde entier	Janine Labrune	67, rue des Cinquante Otages	Nantes	44000	France
19	Eastern Connection	Ann Devon	35 King George	London	WX3 6FW	UK
20	Ernst Handel	Roland Mendel	Kirchgasse 6	Graz	8010	Austria
21	Familia Arquibaldo	Aria Cruz	Rua Orós, 92	São Paulo	05442-030	Brazil
22	FISSA Fabrica Inter. Salchichas S.A.	Diego Roel	C/ Moralzarzal, 86	Madrid	28034	Spain
23	Folies gourmandes	Martine Rancé	184, chaussée de Tournai	Lille	59000	France
24	Folk och fä HB	Maria Larsson	Åkergatan 24	Bräcke	S-844 67	Sweden
25	Frankenversand	Peter Franken	Berliner Platz 43	München	80805	Germany
26	France restauration	Carine Schmitt	54, rue Royale	Nantes	44000	France
27	Franchi S.p.A.	Paolo Accorti	Via Monte Bianco 34	Torino	10100	Italy
28	Furia Bacalhau e Frutos do Mar	Lino Rodriguez	Jardim das rosas n. 32	Lisboa	1675	Portugal
29	Galería del gastrónomo	Eduardo Saavedra	Rambla de Cataluña, 23	Barcelona	08022	Spain
30	Godos Cocina Típica	José Pedro Freyre	C/ Romero, 33	Sevilla	41101	Spain
31	Gourmet Lanchonetes	André Fonseca	Av. Brasil, 442	Campinas	04876-786	Brazil
32	Great Lakes Food Market	Howard Snyder	2732 Baker Blvd.	Eugene	97403	USA
33	GROSELLA-Restaurante	Manuel Pereira	5ª Ave. Los Palos Grandes	Caracas	1081	Venezuela
34	Hanari Carnes	Mario Pontes	Rua do Paço, 67	Rio de Janeiro	05454-876	Brazil
35	HILARIÓN-Abastos	Carlos Hernández	Carrera 22 con Ave. Carlos Soublette #8-35	San Cristóbal	5022	Venezuela
36	Hungry Coyote Import Store	Yoshi Latimer	City Center Plaza 516 Main St.	Elgin	97827	USA
37	Hungry Owl All-Night Grocers	Patricia McKenna	8 Johnstown Road	Cork		Ireland
38	Island Trading	Helen Bennett	Garden House Crowther Way	Cowes	PO31 7PJ	UK
39	Königlich Essen	Philip Cramer	Maubelstr. 90	Brandenburg	14776	Germany
40	La corne d'abondance	Daniel Tonini	67, avenue de l'Europe	Versailles	78000	France
41	La maison d'Asie	Annette Roulet	1 rue Alsace-Lorraine	Toulouse	31000	France
42	Laughing Bacchus Wine Cellars	Yoshi Tannamuri	1900 Oak St.	Vancouver	V3F 2K1	Canada
43	Lazy K Kountry Store	John Steel	12 Orchestra Terrace	Walla Walla	99362	USA
44	Lehmanns Marktstand	Renate Messner	Magazinweg 7	Frankfurt a.M.	60528	Germany
45	Let's Stop N Shop	Jaime Yorres	87 Polk St. Suite 5	San Francisco	94117	USA
46	LILA-Supermercado	Carlos González	Carrera 52 con Ave. Bolívar #65-98 Llano Largo	Barquisimeto	3508	Venezuela
47	LINO-Delicateses	Felipe Izquierdo	Ave. 5 de Mayo Porlamar	I. de Margarita	4980	Venezuela
48	Lonesome Pine Restaurant	Fran Wilson	89 Chiaroscuro Rd.	Portland	97219	USA
49	Magazzini Alimentari Riuniti	Giovanni Rovelli	Via Ludovico il Moro 22	Bergamo	24100	Italy
50	Maison Dewey	Catherine Dewey	Rue Joseph-Bens 532	Bruxelles	B-1180	Belgium
51	Mère Paillarde	Jean Fresnière	43 rue St. Laurent	Montréal	H1J 1C3	Canada
52	Morgenstern Gesundkost	Alexander Feuer	Heerstr. 22	Leipzig	04179	Germany
53	North/South	Simon Crowther	South House 300 Queensbridge	London	SW7 1RZ	UK
54	Océano Atlántico Ltda.	Yvonne Moncada	Ing. Gustavo Moncada 8585 Piso 20-A	Buenos Aires	1010	Argentina
55	Old World Delicatessen	Rene Phillips	2743 Bering St.	Anchorage	99508	USA
56	Ottilies Käseladen	Henriette Pfalzheim	Mehrheimerstr. 369	Köln	50739	Germany
57	Paris spécialités	Marie Bertrand	265, boulevard Charonne	Paris	75012	France
58	Pericles Comidas clásicas	Guillermo Fernández	Calle Dr. Jorge Cash 321	México D.F.	05033	Mexico
59	Piccolo und mehr	Georg Pipps	Geislweg 14	Salzburg	5020	Austria
60	Princesa Isabel Vinhoss	Isabel de Castro	Estrada da saúde n. 58	Lisboa	1756	Portugal
61	Que Delícia	Bernardo Batista	Rua da Panificadora, 12	Rio de Janeiro	02389-673	Brazil
62	Queen Cozinha	Lúcia Carvalho	Alameda dos Canàrios, 891	São Paulo	05487-020	Brazil
63	QUICK-Stop	Horst Kloss	Taucherstraße 10	Cunewalde	01307	Germany
64	Rancho grande	Sergio Gutiérrez	Av. del Libertador 900	Buenos Aires	1010	Argentina
65	Rattlesnake Canyon Grocery	Paula Wilson	2817 Milton Dr.	Albuquerque	87110	USA
66	Reggiani Caseifici	Maurizio Moroni	Strada Provinciale 124	Reggio Emilia	42100	Italy
67	Ricardo Adocicados	Janete Limeira	Av. Copacabana, 267	Rio de Janeiro	02389-890	Brazil
68	Richter Supermarkt	Michael Holz	Grenzacherweg 237	Genève	1203	Switzerland
69	Romero y tomillo	Alejandra Camino	Gran Vía, 1	Madrid	28001	Spain
70	Santé Gourmet	Jonas Bergulfsen	Erling Skakkes gate 78	Stavern	4110	Norway
71	Save-a-lot Markets	Jose Pavarotti	187 Suffolk Ln.	Boise	83720	USA
72	Seven Seas Imports	Hari Kumar	90 Wadhurst Rd.	London	OX15 4NB	UK
73	Simons bistro	Jytte Petersen	Vinbæltet 34	København	1734	Denmark
74	Spécialités du monde	Dominique Perrier	25, rue Lauriston	Paris	75016	France
75	Split Rail Beer & Ale	Art Braunschweiger	P.O. Box 555	Lander	82520	USA
76	Suprêmes délices	Pascale Cartrain	Boulevard Tirou, 255	Charleroi	B-6000	Belgium
77	The Big Cheese	Liz Nixon	89 Jefferson Way Suite 2	Portland	97201	USA
78	The Cracker Box	Liu Wong	55 Grizzly Peak Rd.	Butte	59801	USA
79	Toms Spezialitäten	Karin Josephs	Luisenstr. 48	Münster	44087	Germany
80	Tortuga Restaurante	Miguel Angel Paolino	Avda. Azteca 123	México D.F.	05033	Mexico
81	Tradição Hipermercados	Anabela Domingues	Av. Inês de Castro, 414	São Paulo	05634-030	Brazil
82	Trail's Head Gourmet Provisioners	Helvetius Nagy	722 DaVinci Blvd.	Kirkland	98034	USA
83	Vaffeljernet	Palle Ibsen	Smagsløget 45	Århus	8200	Denmark
84	Victuailles en stock	Mary Saveley	2, rue du Commerce	Lyon	69004	France
85	Vins et alcools Chevalier	Paul Henriot	59 rue de l'Abbaye	Reims	51100	France
86	Die Wandernde Kuh	Rita Müller	Adenauerallee 900	Stuttgart	70563	Germany
87	Wartian Herkku	Pirkko Koskitalo	Torikatu 38	Oulu	90110	Finland
88	Wellington Importadora	Paula Parente	Rua do Mercado, 12	Resende	08737-363	Brazil
89	White Clover Markets	Karl Jablonski	305 - 14th Ave. S. Suite 3B	Seattle	98128	USA
90	Wilman Kala	Matti Karttunen	Keskuskatu 45	Helsinki	21240	Finland
91	Wolski	Zbyszek	ul. Filtrowa 68	Walla	01-012	Poland

Using the % Wildcard

The following SQL statement selects all customers with a City starting with "ber":

Example

SELECT * FROM Customers
WHERE City LIKE 'ber%';

The following SQL statement selects all customers with a City containing the pattern "es":

Example

SELECT * FROM Customers
WHERE City LIKE '%es%';

Using the _ Wildcard

The following SQL statement selects all customers with a City starting with any character, followed by "ondon":

Example

SELECT * FROM Customers
WHERE City LIKE '_ondon';

The following SQL statement selects all customers with a City starting with "L", followed by any character, followed by "n", followed by any character, followed by "on":

Example

SELECT * FROM Customers
WHERE City LIKE 'L_n_on';

Using the [charlist] Wildcard

The following SQL statement selects all customers with a City starting with "b", "s", or "p":

Example

SELECT * FROM Customers
WHERE City LIKE '[bsp]%';

The following SQL statement selects all customers with a City starting with "a", "b", or "c":

Example

SELECT * FROM Customers
WHERE City LIKE '[a-c]%';

Using the [!charlist] Wildcard

The two following SQL statements select all customers with a City NOT starting with "b", "s", or "p":

Example

SELECT * FROM Customers
WHERE City LIKE '[!bsp]%';

Or:

Example

SELECT * FROM Customers
WHERE City NOT LIKE '[bsp]%';

The SQL IN Operator

The IN operator allows you to specify multiple values in a WHERE clause.

The IN operator is a shorthand for multiple OR conditions.

IN Syntax

SELECT column_name(s)
FROM table_name
WHERE column_name IN (value1, value2, ...);

or:

SELECT column_name(s)
FROM table_name
WHERE column_name IN (SELECT STATEMENT);

Demo Database

The table below shows the complete "Customers" table from the Northwind sample database:

CustomerID	CustomerName	ContactName	Address	City	PostalCode	Country
1	Alfreds Futterkiste	Maria Anders	Obere Str. 57	Berlin	12209	Germany
2	Ana Trujillo Emparedados y helados	Ana Trujillo	Avda. de la Constitución 2222	México D.F.	05021	Mexico
3	Antonio Moreno Taquería	Antonio Moreno	Mataderos 2312	México D.F.	05023	Mexico
4	Around the Horn	Thomas Hardy	120 Hanover Sq.	London	WA1 1DP	UK
5	Berglunds snabbköp	Christina Berglund	Berguvsvägen 8	Luleå	S-958 22	Sweden
6	Blauer See Delikatessen	Hanna Moos	Forsterstr. 57	Mannheim	68306	Germany
7	Blondel père et fils	Frédérique Citeaux	24, place Kléber	Strasbourg	67000	France
8	Bólido Comidas preparadas	Martín Sommer	C/ Araquil, 67	Madrid	28023	Spain
9	Bon app'	Laurence Lebihans	12, rue des Bouchers	Marseille	13008	France
10	Bottom-Dollar Marketse	Elizabeth Lincoln	23 Tsawassen Blvd.	Tsawassen	T2F 8M4	Canada
11	B's Beverages	Victoria Ashworth	Fauntleroy Circus	London	EC2 5NT	UK
12	Cactus Comidas para llevar	Patricio Simpson	Cerrito 333	Buenos Aires	1010	Argentina
13	Centro comercial Moctezuma	Francisco Chang	Sierras de Granada 9993	México D.F.	05022	Mexico
14	Chop-suey Chinese	Yang Wang	Hauptstr. 29	Bern	3012	Switzerland
15	Comércio Mineiro	Pedro Afonso	Av. dos Lusíadas, 23	São Paulo	05432-043	Brazil
16	Consolidated Holdings	Elizabeth Brown	Berkeley Gardens 12 Brewery	London	WX1 6LT	UK
17	Drachenblut Delikatessend	Sven Ottlieb	Walserweg 21	Aachen	52066	Germany
18	Du monde entier	Janine Labrune	67, rue des Cinquante Otages	Nantes	44000	France
19	Eastern Connection	Ann Devon	35 King George	London	WX3 6FW	UK
20	Ernst Handel	Roland Mendel	Kirchgasse 6	Graz	8010	Austria
21	Familia Arquibaldo	Aria Cruz	Rua Orós, 92	São Paulo	05442-030	Brazil
22	FISSA Fabrica Inter. Salchichas S.A.	Diego Roel	C/ Moralzarzal, 86	Madrid	28034	Spain
23	Folies gourmandes	Martine Rancé	184, chaussée de Tournai	Lille	59000	France
24	Folk och fä HB	Maria Larsson	Åkergatan 24	Bräcke	S-844 67	Sweden
25	Frankenversand	Peter Franken	Berliner Platz 43	München	80805	Germany
26	France restauration	Carine Schmitt	54, rue Royale	Nantes	44000	France
27	Franchi S.p.A.	Paolo Accorti	Via Monte Bianco 34	Torino	10100	Italy
28	Furia Bacalhau e Frutos do Mar	Lino Rodriguez	Jardim das rosas n. 32	Lisboa	1675	Portugal
29	Galería del gastrónomo	Eduardo Saavedra	Rambla de Cataluña, 23	Barcelona	08022	Spain
30	Godos Cocina Típica	José Pedro Freyre	C/ Romero, 33	Sevilla	41101	Spain
31	Gourmet Lanchonetes	André Fonseca	Av. Brasil, 442	Campinas	04876-786	Brazil
32	Great Lakes Food Market	Howard Snyder	2732 Baker Blvd.	Eugene	97403	USA
33	GROSELLA-Restaurante	Manuel Pereira	5ª Ave. Los Palos Grandes	Caracas	1081	Venezuela
34	Hanari Carnes	Mario Pontes	Rua do Paço, 67	Rio de Janeiro	05454-876	Brazil
35	HILARIÓN-Abastos	Carlos Hernández	Carrera 22 con Ave. Carlos Soublette #8-35	San Cristóbal	5022	Venezuela
36	Hungry Coyote Import Store	Yoshi Latimer	City Center Plaza 516 Main St.	Elgin	97827	USA
37	Hungry Owl All-Night Grocers	Patricia McKenna	8 Johnstown Road	Cork		Ireland
38	Island Trading	Helen Bennett	Garden House Crowther Way	Cowes	PO31 7PJ	UK
39	Königlich Essen	Philip Cramer	Maubelstr. 90	Brandenburg	14776	Germany
40	La corne d'abondance	Daniel Tonini	67, avenue de l'Europe	Versailles	78000	France
41	La maison d'Asie	Annette Roulet	1 rue Alsace-Lorraine	Toulouse	31000	France
42	Laughing Bacchus Wine Cellars	Yoshi Tannamuri	1900 Oak St.	Vancouver	V3F 2K1	Canada
43	Lazy K Kountry Store	John Steel	12 Orchestra Terrace	Walla Walla	99362	USA
44	Lehmanns Marktstand	Renate Messner	Magazinweg 7	Frankfurt a.M.	60528	Germany
45	Let's Stop N Shop	Jaime Yorres	87 Polk St. Suite 5	San Francisco	94117	USA
46	LILA-Supermercado	Carlos González	Carrera 52 con Ave. Bolívar #65-98 Llano Largo	Barquisimeto	3508	Venezuela
47	LINO-Delicateses	Felipe Izquierdo	Ave. 5 de Mayo Porlamar	I. de Margarita	4980	Venezuela
48	Lonesome Pine Restaurant	Fran Wilson	89 Chiaroscuro Rd.	Portland	97219	USA
49	Magazzini Alimentari Riuniti	Giovanni Rovelli	Via Ludovico il Moro 22	Bergamo	24100	Italy
50	Maison Dewey	Catherine Dewey	Rue Joseph-Bens 532	Bruxelles	B-1180	Belgium
51	Mère Paillarde	Jean Fresnière	43 rue St. Laurent	Montréal	H1J 1C3	Canada
52	Morgenstern Gesundkost	Alexander Feuer	Heerstr. 22	Leipzig	04179	Germany
53	North/South	Simon Crowther	South House 300 Queensbridge	London	SW7 1RZ	UK
54	Océano Atlántico Ltda.	Yvonne Moncada	Ing. Gustavo Moncada 8585 Piso 20-A	Buenos Aires	1010	Argentina
55	Old World Delicatessen	Rene Phillips	2743 Bering St.	Anchorage	99508	USA
56	Ottilies Käseladen	Henriette Pfalzheim	Mehrheimerstr. 369	Köln	50739	Germany
57	Paris spécialités	Marie Bertrand	265, boulevard Charonne	Paris	75012	France
58	Pericles Comidas clásicas	Guillermo Fernández	Calle Dr. Jorge Cash 321	México D.F.	05033	Mexico
59	Piccolo und mehr	Georg Pipps	Geislweg 14	Salzburg	5020	Austria
60	Princesa Isabel Vinhoss	Isabel de Castro	Estrada da saúde n. 58	Lisboa	1756	Portugal
61	Que Delícia	Bernardo Batista	Rua da Panificadora, 12	Rio de Janeiro	02389-673	Brazil
62	Queen Cozinha	Lúcia Carvalho	Alameda dos Canàrios, 891	São Paulo	05487-020	Brazil
63	QUICK-Stop	Horst Kloss	Taucherstraße 10	Cunewalde	01307	Germany
64	Rancho grande	Sergio Gutiérrez	Av. del Libertador 900	Buenos Aires	1010	Argentina
65	Rattlesnake Canyon Grocery	Paula Wilson	2817 Milton Dr.	Albuquerque	87110	USA
66	Reggiani Caseifici	Maurizio Moroni	Strada Provinciale 124	Reggio Emilia	42100	Italy
67	Ricardo Adocicados	Janete Limeira	Av. Copacabana, 267	Rio de Janeiro	02389-890	Brazil
68	Richter Supermarkt	Michael Holz	Grenzacherweg 237	Genève	1203	Switzerland
69	Romero y tomillo	Alejandra Camino	Gran Vía, 1	Madrid	28001	Spain
70	Santé Gourmet	Jonas Bergulfsen	Erling Skakkes gate 78	Stavern	4110	Norway
71	Save-a-lot Markets	Jose Pavarotti	187 Suffolk Ln.	Boise	83720	USA
72	Seven Seas Imports	Hari Kumar	90 Wadhurst Rd.	London	OX15 4NB	UK
73	Simons bistro	Jytte Petersen	Vinbæltet 34	København	1734	Denmark
74	Spécialités du monde	Dominique Perrier	25, rue Lauriston	Paris	75016	France
75	Split Rail Beer & Ale	Art Braunschweiger	P.O. Box 555	Lander	82520	USA
76	Suprêmes délices	Pascale Cartrain	Boulevard Tirou, 255	Charleroi	B-6000	Belgium
77	The Big Cheese	Liz Nixon	89 Jefferson Way Suite 2	Portland	97201	USA
78	The Cracker Box	Liu Wong	55 Grizzly Peak Rd.	Butte	59801	USA
79	Toms Spezialitäten	Karin Josephs	Luisenstr. 48	Münster	44087	Germany
80	Tortuga Restaurante	Miguel Angel Paolino	Avda. Azteca 123	México D.F.	05033	Mexico
81	Tradição Hipermercados	Anabela Domingues	Av. Inês de Castro, 414	São Paulo	05634-030	Brazil
82	Trail's Head Gourmet Provisioners	Helvetius Nagy	722 DaVinci Blvd.	Kirkland	98034	USA
83	Vaffeljernet	Palle Ibsen	Smagsløget 45	Århus	8200	Denmark
84	Victuailles en stock	Mary Saveley	2, rue du Commerce	Lyon	69004	France
85	Vins et alcools Chevalier	Paul Henriot	59 rue de l'Abbaye	Reims	51100	France
86	Die Wandernde Kuh	Rita Müller	Adenauerallee 900	Stuttgart	70563	Germany
87	Wartian Herkku	Pirkko Koskitalo	Torikatu 38	Oulu	90110	Finland
88	Wellington Importadora	Paula Parente	Rua do Mercado, 12	Resende	08737-363	Brazil
89	White Clover Markets	Karl Jablonski	305 - 14th Ave. S. Suite 3B	Seattle	98128	USA
90	Wilman Kala	Matti Karttunen	Keskuskatu 45	Helsinki	21240	Finland
91	Wolski	Zbyszek	ul. Filtrowa 68	Walla	01-012	Poland

IN Operator Examples

The following SQL statement selects all customers that are located in "Germany", "France" or "UK":

Example

SELECT * FROM Customers
WHERE Country IN ('Germany', 'France', 'UK');

The following SQL statement selects all customers that are NOT located in "Germany", "France" or "UK":

Example

SELECT * FROM Customers
WHERE Country NOT IN ('Germany', 'France', 'UK');

The following SQL statement selects all customers that are from the same countries as the suppliers:

Example

SELECT * FROM Customers
WHERE Country IN (SELECT Country FROM Suppliers);

The SQL BETWEEN Operator

The BETWEEN operator selects values within a given range. The values can be numbers, text, or dates.

The BETWEEN operator is inclusive: begin and end values are included.

BETWEEN Syntax

SELECT column_name(s)
FROM table_name
WHERE column_name BETWEEN value1 AND value2;

Demo Database

Below is a selection from the "Products" table in the Northwind sample database:

ProductID	ProductName	SupplierID	CategoryID	Unit	Price
1	Chais	1	1	10 boxes x 20 bags	18
2	Chang	1	1	24 - 12 oz bottles	19
3	Aniseed Syrup	1	2	12 - 550 ml bottles	10
4	Chef Anton's Cajun Seasoning	1	2	48 - 6 oz jars	22
5	Chef Anton's Gumbo Mix	1	2	36 boxes	21.35

BETWEEN Example

The following SQL statement selects all products with a price between 10 and 20:

Example

SELECT * FROM Products
WHERE Price BETWEEN 10 AND 20;

NOT BETWEEN Example

To display the products outside the range of the previous example, use NOT BETWEEN:

Example

SELECT * FROM Products
WHERE Price NOT BETWEEN 10 AND 20;

BETWEEN with IN Example

The following SQL statement selects all products with a price between 10 and 20. In addition; do not show products with a CategoryID of 1,2, or 3:

Example

SELECT * FROM Products
WHERE Price BETWEEN 10 AND 20
AND CategoryID NOT IN (1,2,3);

BETWEEN Text Values Example

The following SQL statement selects all products with a ProductName between Carnarvon Tigers and Mozzarella di Giovanni:

Example

SELECT * FROM Products
WHERE ProductName BETWEEN 'Carnarvon Tigers' AND 'Mozzarella di Giovanni'
ORDER BY ProductName;

The following SQL statement selects all products with a ProductName between Carnarvon Tigers and Chef Anton's Cajun Seasoning:

Example

SELECT * FROM Products
WHERE ProductName BETWEEN "Carnarvon Tigers" AND "Chef Anton's Cajun Seasoning"
ORDER BY ProductName;

NOT BETWEEN Text Values Example

The following SQL statement selects all products with a ProductName not between Carnarvon Tigers and Mozzarella di Giovanni:

Example

SELECT * FROM Products
WHERE ProductName NOT BETWEEN 'Carnarvon Tigers' AND 'Mozzarella di Giovanni'
ORDER BY ProductName;

Sample Table

Below is a selection from the "Orders" table in the Northwind sample database:

OrderID	CustomerID	EmployeeID	OrderDate	ShipperID
10248	90	5	7/4/1996	3
10249	81	6	7/5/1996	1
10250	34	4	7/8/1996	2
10251	84	3	7/9/1996	1
10252	76	4	7/10/1996	2

BETWEEN Dates Example

The following SQL statement selects all orders with an OrderDate between '01-July-1996' and '31-July-1996':

Example

SELECT * FROM Orders
WHERE OrderDate BETWEEN #07/01/1996# AND #07/31/1996#;

OR:

Example

SELECT * FROM Orders
WHERE OrderDate BETWEEN '1996-07-01' AND '1996-07-31';

SQL Aliases

SQL aliases are used to give a table, or a column in a table, a temporary name.

Aliases are often used to make column names more readable.

An alias only exists for the duration of that query.

An alias is created with the AS keyword.

Alias Column Syntax

SELECT column_name AS alias_name
FROM table_name;

Alias Table Syntax

SELECT column_name(s)
FROM table_name AS alias_name;

Demo Database

In this tutorial we will use the well-known Northwind sample database.

Below is a selection from the "Customers" table:

CustomerID	CustomerName	ContactName	Address	City	PostalCode	Country
2	Ana Trujillo Emparedados y helados	Ana Trujillo	Avda. de la Constitución 2222	México D.F.	05021	Mexico
3	Antonio Moreno Taquería	Antonio Moreno	Mataderos 2312	México D.F.	05023	Mexico
4	Around the Horn	Thomas Hardy	120 Hanover Sq.	London	WA1 1DP	UK

And a selection from the "Orders" table:

OrderID	CustomerID	EmployeeID	OrderDate	ShipperID
10354	58	8	1996-11-14	3
10355	4	6	1996-11-15	1
10356	86	6	1996-11-18	2

Alias for Columns Examples

The following SQL statement creates two aliases, one for the CustomerID column and one for the CustomerName column:

Example

SELECT CustomerID AS ID, CustomerName AS Customer
FROM Customers;

The following SQL statement creates two aliases, one for the CustomerName column and one for the ContactName column. Note: It requires double quotation marks or square brackets if the alias name contains spaces:

Example

SELECT CustomerName AS Customer, ContactName AS [Contact Person]
FROM Customers;

The following SQL statement creates an alias named "Address" that combine four columns (Address, PostalCode, City and Country):

Example

SELECT CustomerName, Address + ', ' + PostalCode + ' ' + City + ', ' + Country AS Address
FROM Customers;

Note: To get the SQL statement above to work in MySQL use the following:

SELECT CustomerName, CONCAT(Address,', ',PostalCode,', ',City,', ',Country) AS Address
FROM Customers;

Note: To get the SQL statement above to work in Oracle use the following:

SELECT CustomerName, (Address || ', ' || PostalCode || ' ' || City || ', ' || Country) AS Address
FROM Customers;

Alias for Tables Example

The following SQL statement selects all the orders from the customer with CustomerID=4 (Around the Horn). We use the "Customers" and "Orders" tables, and give them the table aliases of "c" and "o" respectively (Here we use aliases to make the SQL shorter):

Example

SELECT o.OrderID, o.OrderDate, c.CustomerName
FROM Customers AS c, Orders AS o
WHERE c.CustomerName='Around the Horn' AND c.CustomerID=o.CustomerID;

The following SQL statement is the same as above, but without aliases:

Example

SELECT Orders.OrderID, Orders.OrderDate, Customers.CustomerName
FROM Customers, Orders
WHERE Customers.CustomerName='Around the Horn' AND Customers.CustomerID=Orders.CustomerID;

Aliases can be useful when:

There are more than one table involved in a query
Functions are used in the query
Column names are big or not very readable
Two or more columns are combined together

SQL Joins

SQL JOIN

A JOIN clause is used to combine rows from two or more tables, based on a related column between them.

Let's look at a selection from the "Orders" table:

OrderID	CustomerID	OrderDate
10308	2	1996-09-18
10309	37	1996-09-19
10310	77	1996-09-20

Then, look at a selection from the "Customers" table:

CustomerID	CustomerName	ContactName	Country
1	Alfreds Futterkiste	Maria Anders	Germany
2	Ana Trujillo Emparedados y helados	Ana Trujillo	Mexico
3	Antonio Moreno Taquería	Antonio Moreno	Mexico

Notice that the "CustomerID" column in the "Orders" table refers to the "CustomerID" in the "Customers" table. The relationship between the two tables above is the "CustomerID" column.

Then, we can create the following SQL statement (that contains an INNER JOIN), that selects records that have matching values in both tables:

Example

SELECT Orders.OrderID, Customers.CustomerName, Orders.OrderDate
FROM Orders
INNER JOIN Customers ON Orders.CustomerID=Customers.CustomerID;

and it will produce something like this:

OrderID	CustomerName	OrderDate
10308	Ana Trujillo Emparedados y helados	9/18/1996
10365	Antonio Moreno Taquería	11/27/1996
10383	Around the Horn	12/16/1996
10355	Around the Horn	11/15/1996
10278	Berglunds snabbköp	8/12/1996

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Different Types of SQL JOINs

Here are the different types of the JOINs in SQL:

(INNER) JOIN: Returns records that have matching values in both tables
LEFT (OUTER) JOIN: Returns all records from the left table, and the matched records from the right table
RIGHT (OUTER) JOIN: Returns all records from the right table, and the matched records from the left table
FULL (OUTER) JOIN: Returns all records when there is a match in either left or right table

SQL INNER JOIN SQL LEFT JOIN SQL RIGHT JOIN SQL FULL OUTER JOIN

SQL INNER JOIN Keyword

The INNER JOIN keyword selects records that have matching values in both tables.

INNER JOIN Syntax

SELECT column_name(s)
FROM table1
INNER JOIN table2
ON table1.column_name = table2.column_name;

SQL INNER JOIN

Demo Database

In this tutorial we will use the well-known Northwind sample database.

Below is a selection from the "Orders" table:

OrderID	CustomerID	EmployeeID	OrderDate	ShipperID
10308	2	7	1996-09-18	3
10309	37	3	1996-09-19	1
10310	77	8	1996-09-20	2

And a selection from the "Customers" table:

CustomerID	CustomerName	ContactName	Address	City	PostalCode	Country
1	Alfreds Futterkiste	Maria Anders	Obere Str. 57	Berlin	12209	Germany
2	Ana Trujillo Emparedados y helados	Ana Trujillo	Avda. de la Constitución 2222	México D.F.	05021	Mexico
3	Antonio Moreno Taquería	Antonio Moreno	Mataderos 2312	México D.F.	05023	Mexico

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SQL INNER JOIN Example

The following SQL statement selects all orders with customer information:

Example

SELECT Orders.OrderID, Customers.CustomerName
FROM Orders
INNER JOIN Customers ON Orders.CustomerID = Customers.CustomerID;

Note: The INNER JOIN keyword selects all rows from both tables as long as there is a match between the columns. If there are records in the "Orders" table that do not have matches in "Customers", these orders will not be shown!

JOIN Three Tables

The following SQL statement selects all orders with customer and shipper information:

Example

SELECT Orders.OrderID, Customers.CustomerName, Shippers.ShipperName
FROM ((Orders
INNER JOIN Customers ON Orders.CustomerID = Customers.CustomerID)
INNER JOIN Shippers ON Orders.ShipperID = Shippers.ShipperID);

SQL LEFT JOIN Keyword

The LEFT JOIN keyword returns all records from the left table (table1), and the matching records from the right table (table2). The result is 0 records from the right side, if there is no match.

LEFT JOIN Syntax

SELECT column_name(s)
FROM table1
LEFT JOIN table2
ON table1.column_name = table2.column_name;

Note: In some databases LEFT JOIN is called LEFT OUTER JOIN.

SQL LEFT JOIN

Demo Database

In this tutorial we will use the well-known Northwind sample database.

Below is a selection from the "Customers" table:

CustomerID	CustomerName	ContactName	Address	City	PostalCode	Country
1	Alfreds Futterkiste	Maria Anders	Obere Str. 57	Berlin	12209	Germany
2	Ana Trujillo Emparedados y helados	Ana Trujillo	Avda. de la Constitución 2222	México D.F.	05021	Mexico
3	Antonio Moreno Taquería	Antonio Moreno	Mataderos 2312	México D.F.	05023	Mexico

And a selection from the "Orders" table:

OrderID	CustomerID	EmployeeID	OrderDate	ShipperID
10308	2	7	1996-09-18	3
10309	37	3	1996-09-19	1
10310	77	8	1996-09-20	2

SQL LEFT JOIN Example

The following SQL statement will select all customers, and any orders they might have:

Example

SELECT Customers.CustomerName, Orders.OrderID
FROM Customers
LEFT JOIN Orders ON Customers.CustomerID = Orders.CustomerID
ORDER BY Customers.CustomerName;

Note: The LEFT JOIN keyword returns all records from the left table (Customers), even if there are no matches in the right table (Orders).

SQL RIGHT JOIN Keyword

The RIGHT JOIN keyword returns all records from the right table (table2), and the matching records from the left table (table1). The result is 0 records from the left side, if there is no match.

RIGHT JOIN Syntax

SELECT column_name(s)
FROM table1
RIGHT JOIN table2
ON table1.column_name = table2.column_name;

Note: In some databases RIGHT JOIN is called RIGHT OUTER JOIN.

SQL RIGHT JOIN

Demo Database

In this tutorial we will use the well-known Northwind sample database.

Below is a selection from the "Orders" table:

OrderID	CustomerID	EmployeeID	OrderDate	ShipperID
10308	2	7	1996-09-18	3
10309	37	3	1996-09-19	1
10310	77	8	1996-09-20	2

And a selection from the "Employees" table:

EmployeeID	LastName	FirstName	BirthDate	Photo
1	Davolio	Nancy	12/8/1968	EmpID1.pic
2	Fuller	Andrew	2/19/1952	EmpID2.pic
3	Leverling	Janet	8/30/1963	EmpID3.pic

SQL RIGHT JOIN Example

The following SQL statement will return all employees, and any orders they might have placed:

Example

SELECT Orders.OrderID, Employees.LastName, Employees.FirstName
FROM Orders
RIGHT JOIN Employees ON Orders.EmployeeID = Employees.EmployeeID
ORDER BY Orders.OrderID;

Note: The RIGHT JOIN keyword returns all records from the right table (Employees), even if there are no matches in the left table (Orders).

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SQL FULL OUTER JOIN Keyword

The FULL OUTER JOIN keyword returns all records when there is a match in left (table1) or right (table2) table records.

Tip: FULL OUTER JOIN and FULL JOIN are the same.

FULL OUTER JOIN Syntax

SELECT column_name(s)
FROM table1
FULL OUTER JOIN table2
ON table1.column_name = table2.column_name
WHERE condition;

SQL FULL OUTER JOIN

Note: FULL OUTER JOIN can potentially return very large result-sets!

Demo Database

In this tutorial we will use the well-known Northwind sample database.

Below is a selection from the "Customers" table:

CustomerID	CustomerName	ContactName	Address	City	PostalCode	Country
1	Alfreds Futterkiste	Maria Anders	Obere Str. 57	Berlin	12209	Germany
2	Ana Trujillo Emparedados y helados	Ana Trujillo	Avda. de la Constitución 2222	México D.F.	05021	Mexico
3	Antonio Moreno Taquería	Antonio Moreno	Mataderos 2312	México D.F.	05023	Mexico

And a selection from the "Orders" table:

OrderID	CustomerID	EmployeeID	OrderDate	ShipperID
10308	2	7	1996-09-18	3
10309	37	3	1996-09-19	1
10310	77	8	1996-09-20	2

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SQL FULL OUTER JOIN Example

The following SQL statement selects all customers, and all orders:

SELECT Customers.CustomerName, Orders.OrderID
FROM Customers
FULL OUTER JOIN Orders ON Customers.CustomerID=Orders.CustomerID
ORDER BY Customers.CustomerName;

A selection from the result set may look like this:

CustomerName	OrderID
Null	10309
Null	10310
Alfreds Futterkiste	Null
Ana Trujillo Emparedados y helados	10308
Antonio Moreno Taquería	Null

Note: The FULL OUTER JOIN keyword returns all matching records from both tables whether the other table matches or not. So, if there are rows in "Customers" that do not have matches in "Orders", or if there are rows in "Orders" that do not have matches in "Customers", those rows will be listed as well.

SQL Self Join

A self join is a regular join, but the table is joined with itself.

Self Join Syntax

SELECT column_name(s)
FROM table1 T1, table1 T2
WHERE condition;

T1 and T2 are different table aliases for the same table.

Demo Database

In this tutorial we will use the well-known Northwind sample database.

Below is a selection from the "Customers" table:

CustomerID	CustomerName	ContactName	Address	City	PostalCode	Country
1	Alfreds Futterkiste	Maria Anders	Obere Str. 57	Berlin	12209	Germany
2	Ana Trujillo Emparedados y helados	Ana Trujillo	Avda. de la Constitución 2222	México D.F.	05021	Mexico
3	Antonio Moreno Taquería	Antonio Moreno	Mataderos 2312	México D.F.	05023	Mexico

SQL Self Join Example

The following SQL statement matches customers that are from the same city:

Example

SELECT A.CustomerName AS CustomerName1, B.CustomerName AS CustomerName2, A.City
FROM Customers A, Customers B
WHERE A.CustomerID <> B.CustomerID
AND A.City = B.City
ORDER BY A.City;

The SQL UNION Operator

The UNION operator is used to combine the result-set of two or more SELECT statements.

Every SELECT statement within UNION must have the same number of columns
The columns must also have similar data types
The columns in every SELECT statement must also be in the same order

UNION Syntax

SELECT column_name(s) FROM table1
UNION
SELECT column_name(s) FROM table2;

UNION ALL Syntax

The UNION operator selects only distinct values by default. To allow duplicate values, use UNION ALL:

SELECT column_name(s) FROM table1
UNION ALL
SELECT column_name(s) FROM table2;

Note: The column names in the result-set are usually equal to the column names in the first SELECT statement.

Demo Database

In this tutorial we will use the well-known Northwind sample database.

Below is a selection from the "Customers" table:

CustomerID	CustomerName	ContactName	Address	City	PostalCode	Country
1	Alfreds Futterkiste	Maria Anders	Obere Str. 57	Berlin	12209	Germany
2	Ana Trujillo Emparedados y helados	Ana Trujillo	Avda. de la Constitución 2222	México D.F.	05021	Mexico
3	Antonio Moreno Taquería	Antonio Moreno	Mataderos 2312	México D.F.	05023	Mexico

And a selection from the "Suppliers" table:

SupplierID	SupplierName	ContactName	Address	City	PostalCode	Country
1	Exotic Liquid	Charlotte Cooper	49 Gilbert St.	London	EC1 4SD	UK
2	New Orleans Cajun Delights	Shelley Burke	P.O. Box 78934	New Orleans	70117	USA
3	Grandma Kelly's Homestead	Regina Murphy	707 Oxford Rd.	Ann Arbor	48104	USA

SQL UNION Example

The following SQL statement returns the cities (only distinct values) from both the "Customers" and the "Suppliers" table:

Example

SELECT City FROM Customers
UNION
SELECT City FROM Suppliers
ORDER BY City;

Note: If some customers or suppliers have the same city, each city will only be listed once, because UNION selects only distinct values. Use UNION ALL to also select duplicate values!

SQL UNION ALL Example

The following SQL statement returns the cities (duplicate values also) from both the "Customers" and the "Suppliers" table:

Example

SELECT City FROM Customers
UNION ALL
SELECT City FROM Suppliers
ORDER BY City;

SQL UNION With WHERE

The following SQL statement returns the German cities (only distinct values) from both the "Customers" and the "Suppliers" table:

Example

SELECT City, Country FROM Customers
WHERE Country='Germany'
UNION
SELECT City, Country FROM Suppliers
WHERE Country='Germany'
ORDER BY City;

SQL UNION ALL With WHERE

The following SQL statement returns the German cities (duplicate values also) from both the "Customers" and the "Suppliers" table:

Example

SELECT City, Country FROM Customers
WHERE Country='Germany'
UNION ALL
SELECT City, Country FROM Suppliers
WHERE Country='Germany'
ORDER BY City;

Another UNION Example

The following SQL statement lists all customers and suppliers:

Example

SELECT 'Customer' AS Type, ContactName, City, Country
FROM Customers
UNION
SELECT 'Supplier', ContactName, City, Country
FROM Suppliers;

Notice the "AS Type" above - it is an alias. are used to give a table or a column a temporary name. An alias only exists for the duration of the query. So, here we have created a temporary column named "Type", that list whether the contact person is a "Customer" or a "Supplier".

The SQL GROUP BY Statement

The GROUP BY statement groups rows that have the same values into summary rows, like "find the number of customers in each country".

The GROUP BY statement is often used with aggregate functions (COUNT(), MAX(), MIN(), SUM(), AVG()) to group the result-set by one or more columns.

GROUP BY Syntax

SELECT column_name(s)
FROM table_name
WHERE condition
GROUP BY column_name(s)
ORDER BY column_name(s);

Demo Database

Below is a selection from the "Customers" table in the Northwind sample database:

CustomerID	CustomerName	ContactName	Address	City	PostalCode	Country
1	Alfreds Futterkiste	Maria Anders	Obere Str. 57	Berlin	12209	Germany
2	Ana Trujillo Emparedados y helados	Ana Trujillo	Avda. de la Constitución 2222	México D.F.	05021	Mexico
3	Antonio Moreno Taquería	Antonio Moreno	Mataderos 2312	México D.F.	05023	Mexico
4	Around the Horn	Thomas Hardy	120 Hanover Sq.	London	WA1 1DP	UK
5	Berglunds snabbköp	Christina Berglund	Berguvsvägen 8	Luleå	S-958 22	Sweden

SQL GROUP BY Examples

The following SQL statement lists the number of customers in each country:

Example

SELECT COUNT(CustomerID), Country
FROM Customers
GROUP BY Country;

The following SQL statement lists the number of customers in each country, sorted high to low:

Example

SELECT COUNT(CustomerID), Country
FROM Customers
GROUP BY Country
ORDER BY COUNT(CustomerID) DESC;

Demo Database

Below is a selection from the "Orders" table in the Northwind sample database:

OrderID	CustomerID	EmployeeID	OrderDate	ShipperID
10248	90	5	1996-07-04	3
10249	81	6	1996-07-05	1
10250	34	4	1996-07-08	2

And a selection from the "Shippers" table:

ShipperID	ShipperName
1	Speedy Express
2	United Package
3	Federal Shipping

GROUP BY With JOIN Example

The following SQL statement lists the number of orders sent by each shipper:

Example

SELECT Shippers.ShipperName, COUNT(Orders.OrderID) AS NumberOfOrders FROM Orders
LEFT JOIN Shippers ON Orders.ShipperID = Shippers.ShipperID
GROUP BY ShipperName;

The SQL HAVING Clause

The HAVING clause was added to SQL because the WHERE keyword cannot be used with aggregate functions.

HAVING Syntax

SELECT column_name(s)
FROM table_name
WHERE condition
GROUP BY column_name(s)
HAVING condition
ORDER BY column_name(s);

Demo Database

Below is a selection from the "Customers" table in the Northwind sample database:

CustomerID	CustomerName	ContactName	Address	City	PostalCode	Country
1	Alfreds Futterkiste	Maria Anders	Obere Str. 57	Berlin	12209	Germany
2	Ana Trujillo Emparedados y helados	Ana Trujillo	Avda. de la Constitución 2222	México D.F.	05021	Mexico
3	Antonio Moreno Taquería	Antonio Moreno	Mataderos 2312	México D.F.	05023	Mexico
4	Around the Horn	Thomas Hardy	120 Hanover Sq.	London	WA1 1DP	UK
5	Berglunds snabbköp	Christina Berglund	Berguvsvägen 8	Luleå	S-958 22	Sweden

SQL HAVING Examples

The following SQL statement lists the number of customers in each country. Only include countries with more than 5 customers:

Example

SELECT COUNT(CustomerID), Country
FROM Customers
GROUP BY Country
HAVING COUNT(CustomerID) > 5;

The following SQL statement lists the number of customers in each country, sorted high to low (Only include countries with more than 5 customers):

Example

SELECT COUNT(CustomerID), Country
FROM Customers
GROUP BY Country
HAVING COUNT(CustomerID) > 5
ORDER BY COUNT(CustomerID) DESC;

Demo Database

Below is a selection from the "Orders" table in the Northwind sample database:

OrderID	CustomerID	EmployeeID	OrderDate	ShipperID
10248	90	5	1996-07-04	3
10249	81	6	1996-07-05	1
10250	34	4	1996-07-08	2

And a selection from the "Employees" table:

EmployeeID	LastName	FirstName	BirthDate	Photo	Notes
1	Davolio	Nancy	1968-12-08	EmpID1.pic	Education includes a BA....
2	Fuller	Andrew	1952-02-19	EmpID2.pic	Andrew received his BTS....
3	Leverling	Janet	1963-08-30	EmpID3.pic	Janet has a BS degree....

More HAVING Examples

The following SQL statement lists the employees that have registered more than 10 orders:

Example

SELECT Employees.LastName, COUNT(Orders.OrderID) AS NumberOfOrders
FROM (Orders
INNER JOIN Employees ON Orders.EmployeeID = Employees.EmployeeID)
GROUP BY LastName
HAVING COUNT(Orders.OrderID) > 10;

The following SQL statement lists if the employees "Davolio" or "Fuller" have registered more than 25 orders:

Example

SELECT Employees.LastName, COUNT(Orders.OrderID) AS NumberOfOrders
FROM Orders
INNER JOIN Employees ON Orders.EmployeeID = Employees.EmployeeID
WHERE LastName = 'Davolio' OR LastName = 'Fuller'
GROUP BY LastName
HAVING COUNT(Orders.OrderID) > 25;

SQL EXISTS Operator

The SQL EXISTS Operator

The EXISTS operator is used to test for the existence of any record in a subquery.

The EXISTS operator returns TRUE if the subquery returns one or more records.

EXISTS Syntax

SELECT column_name(s)
FROM table_name
WHERE EXISTS
(SELECT column_name FROM table_name WHERE condition);

Demo Database

Below is a selection from the "Products" table in the Northwind sample database:

ProductID	ProductName	SupplierID	CategoryID	Unit	Price
1	Chais	1	1	10 boxes x 20 bags	18
2	Chang	1	1	24 - 12 oz bottles	19
3	Aniseed Syrup	1	2	12 - 550 ml bottles	10
4	Chef Anton's Cajun Seasoning	2	2	48 - 6 oz jars	22
5	Chef Anton's Gumbo Mix	2	2	36 boxes	21.35

And a selection from the "Suppliers" table:

SupplierID	SupplierName	ContactName	Address	City	PostalCode	Country
1	Exotic Liquid	Charlotte Cooper	49 Gilbert St.	London	EC1 4SD	UK
2	New Orleans Cajun Delights	Shelley Burke	P.O. Box 78934	New Orleans	70117	USA
3	Grandma Kelly's Homestead	Regina Murphy	707 Oxford Rd.	Ann Arbor	48104	USA
4	Tokyo Traders	Yoshi Nagase	9-8 Sekimai Musashino-shi	Tokyo	100	Japan

SQL EXISTS Examples

The following SQL statement returns TRUE and lists the suppliers with a product price less than 20:

Example

SELECT SupplierName
FROM Suppliers
WHERE EXISTS (SELECT ProductName FROM Products WHERE Products.SupplierID = Suppliers.supplierID AND Price < 20);

The following SQL statement returns TRUE and lists the suppliers with a product price equal to 22:

Example

SELECT SupplierName
FROM Suppliers
WHERE EXISTS (SELECT ProductName FROM Products WHERE Products.SupplierID = Suppliers.supplierID AND Price = 22);

SQL ANY and ALL Operators

The SQL ANY and ALL Operators

The ANY and ALL operators allow you to perform a comparison between a single column value and a range of other values.

The SQL ANY Operator

The ANY operator:

returns a boolean value as a result
returns TRUE if ANY of the subquery values meet the condition

ANY means that the condition will be true if the operation is true for any of the values in the range.

ANY Syntax

SELECT column_name(s)
FROM table_name
WHERE column_name operator ANY
(SELECT column_name
FROM table_name
WHERE condition);

Note: The operator must be a standard comparison operator (=, <>, !=, >, >=, <, or <=).

The SQL ALL Operator

The ALL operator:

returns a boolean value as a result
returns TRUE if ALL of the subquery values meet the condition
is used with SELECT, WHERE and HAVING statements

ALL means that the condition will be true only if the operation is true for all values in the range.

ALL Syntax With SELECT

SELECT ALL column_name(s)
FROM table_name
WHERE condition;

ALL Syntax With WHERE or HAVING

SELECT column_name(s)
FROM table_name
WHERE column_name operator ALL
(SELECT column_name
FROM table_name
WHERE condition);

Note: The operator must be a standard comparison operator (=, <>, !=, >, >=, <, or <=).

Demo Database

Below is a selection from the "Products" table in the Northwind sample database:

ProductID	ProductName	SupplierID	CategoryID	Unit	Price
1	Chais	1	1	10 boxes x 20 bags	18
2	Chang	1	1	24 - 12 oz bottles	19
3	Aniseed Syrup	1	2	12 - 550 ml bottles	10
4	Chef Anton's Cajun Seasoning	2	2	48 - 6 oz jars	22
5	Chef Anton's Gumbo Mix	2	2	36 boxes	21.35
6	Grandma's Boysenberry Spread	3	2	12 - 8 oz jars	25
7	Uncle Bob's Organic Dried Pears	3	7	12 - 1 lb pkgs.	30
8	Northwoods Cranberry Sauce	3	2	12 - 12 oz jars	40
9	Mishi Kobe Niku	4	6	18 - 500 g pkgs.	97

And a selection from the "OrderDetails" table:

OrderDetailID	OrderID	ProductID	Quantity
1	10248	11	12
2	10248	42	10
3	10248	72	5
4	10249	14	9
5	10249	51	40
6	10250	41	10
7	10250	51	35
8	10250	65	15
9	10251	22	6
10	10251	57	15

SQL ANY Examples

The following SQL statement lists the ProductName if it finds ANY records in the OrderDetails table has Quantity equal to 10 (this will return TRUE because the Quantity column has some values of 10):

Example

SELECT ProductName
FROM Products
WHERE ProductID = ANY
(SELECT ProductID
FROM OrderDetails
WHERE Quantity = 10);

The following SQL statement lists the ProductName if it finds ANY records in the OrderDetails table has Quantity larger than 99 (this will return TRUE because the Quantity column has some values larger than 99):

Example

SELECT ProductName
FROM Products
WHERE ProductID = ANY
(SELECT ProductID
FROM OrderDetails
WHERE Quantity > 99);

The following SQL statement lists the ProductName if it finds ANY records in the OrderDetails table has Quantity larger than 1000 (this will return FALSE because the Quantity column has no values larger than 1000):

Example

SELECT ProductName
FROM Products
WHERE ProductID = ANY
(SELECT ProductID
FROM OrderDetails
WHERE Quantity > 1000);

SQL ALL Examples

The following SQL statement lists ALL the product names:

Example

SELECT ALL ProductName
FROM Products
WHERE TRUE;

The following SQL statement lists the ProductName if ALL the records in the OrderDetails table has Quantity equal to 10. This will of course return FALSE because the Quantity column has many different values (not only the value of 10):

Example

SELECT ProductName
FROM Products
WHERE ProductID = ALL
(SELECT ProductID
FROM OrderDetails
WHERE Quantity = 10);

The SQL SELECT INTO Statement

The SELECT INTO statement copies data from one table into a new table.

SELECT INTO Syntax

Copy all columns into a new table:

SELECT *
INTO newtable [IN externaldb]
FROM oldtable
WHERE condition;

Copy only some columns into a new table:

SELECT column1, column2, column3, ...
INTO newtable [IN externaldb]
FROM oldtable
WHERE condition;

The new table will be created with the column-names and types as defined in the old table. You can create new column names using the AS clause.

SQL SELECT INTO Examples

The following SQL statement creates a backup copy of Customers:

SELECT * INTO CustomersBackup2017
FROM Customers;

The following SQL statement uses the IN clause to copy the table into a new table in another database:

SELECT * INTO CustomersBackup2017 IN 'Backup.mdb'
FROM Customers;

The following SQL statement copies only a few columns into a new table:

SELECT CustomerName, ContactName INTO CustomersBackup2017
FROM Customers;

The following SQL statement copies only the German customers into a new table:

SELECT * INTO CustomersGermany
FROM Customers
WHERE Country = 'Germany';

The following SQL statement copies data from more than one table into a new table:

SELECT Customers.CustomerName, Orders.OrderID
INTO CustomersOrderBackup2017
FROM Customers
LEFT JOIN Orders ON Customers.CustomerID = Orders.CustomerID;

Tip: SELECT INTO can also be used to create a new, empty table using the schema of another. Just add a WHERE clause that causes the query to return no data:

SELECT * INTO newtable
FROM oldtable
WHERE 1 = 0;

The SQL INSERT INTO SELECT Statement

The INSERT INTO SELECT statement copies data from one table and inserts it into another table.

The INSERT INTO SELECT statement requires that the data types in source and target tables match.

Note: The existing records in the target table are unaffected.

INSERT INTO SELECT Syntax

Copy all columns from one table to another table:

INSERT INTO table2
SELECT * FROM table1
WHERE condition;

Copy only some columns from one table into another table:

INSERT INTO table2 (column1, column2, column3, ...)
SELECT column1, column2, column3, ...
FROM table1
WHERE condition;

Demo Database

In this tutorial we will use the well-known Northwind sample database.

Below is a selection from the "Customers" table:

CustomerID	CustomerName	ContactName	Address	City	PostalCode	Country
1	Alfreds Futterkiste	Maria Anders	Obere Str. 57	Berlin	12209	Germany
2	Ana Trujillo Emparedados y helados	Ana Trujillo	Avda. de la Constitución 2222	México D.F.	05021	Mexico
3	Antonio Moreno Taquería	Antonio Moreno	Mataderos 2312	México D.F.	05023	Mexico

And a selection from the "Suppliers" table:

SupplierID	SupplierName	ContactName	Address	City	Postal Code	Country
1	Exotic Liquid	Charlotte Cooper	49 Gilbert St.	Londona	EC1 4SD	UK
2	New Orleans Cajun Delights	Shelley Burke	P.O. Box 78934	New Orleans	70117	USA
3	Grandma Kelly's Homestead	Regina Murphy	707 Oxford Rd.	Ann Arbor	48104	USA

SQL INSERT INTO SELECT Examples

The following SQL statement copies "Suppliers" into "Customers" (the columns that are not filled with data, will contain NULL):

Example

INSERT INTO Customers (CustomerName, City, Country)
SELECT SupplierName, City, Country FROM Suppliers;

The following SQL statement copies "Suppliers" into "Customers" (fill all columns):

Example

INSERT INTO Customers (CustomerName, ContactName, Address, City, PostalCode, Country)
SELECT SupplierName, ContactName, Address, City, PostalCode, Country FROM Suppliers;

The following SQL statement copies only the German suppliers into "Customers":

Example

INSERT INTO Customers (CustomerName, City, Country)
SELECT SupplierName, City, Country FROM Suppliers
WHERE Country='Germany';

The SQL CASE Expression

The CASE expression goes through conditions and returns a value when the first condition is met (like an if-then-else statement). So, once a condition is true, it will stop reading and return the result. If no conditions are true, it returns the value in the ELSE clause.

If there is no ELSE part and no conditions are true, it returns NULL.

CASE Syntax

CASE
    WHEN condition1 THEN result1
    WHEN condition2 THEN result2
    WHEN conditionN THEN resultN
    ELSE result
END;

Demo Database

Below is a selection from the "OrderDetails" table in the Northwind sample database:

OrderDetailID	OrderID	ProductID	Quantity
1	10248	11	12
2	10248	42	10
3	10248	72	5
4	10249	14	9
5	10249	51	40

SQL CASE Examples

The following SQL goes through conditions and returns a value when the first condition is met:

Example

SELECT OrderID, Quantity,
CASE
    WHEN Quantity > 30 THEN 'The quantity is greater than 30'
    WHEN Quantity = 30 THEN 'The quantity is 30'
    ELSE 'The quantity is under 30'
END AS QuantityText
FROM OrderDetails;

The following SQL will order the customers by City. However, if City is NULL, then order by Country:

Example

SELECT CustomerName, City, Country
FROM Customers
ORDER BY
(CASE
WHEN City IS NULL THEN Country
ELSE City
END);

SQL IFNULL(), ISNULL(), COALESCE(), and NVL() Functions

Look at the following "Products" table:

P_Id	ProductName	UnitPrice	UnitsInStock	UnitsOnOrder
1	Jarlsberg	10.45	16	15
2	Mascarpone	32.56	23
3	Gorgonzola	15.67	9	20

Suppose that the "UnitsOnOrder" column is optional, and may contain NULL values.

Look at the following SELECT statement:

SELECT ProductName, UnitPrice * (UnitsInStock + UnitsOnOrder)
FROM Products;

In the example above, if any of the "UnitsOnOrder" values are NULL, the result will be NULL.

Solutions

MySQL

The MySQL function lets you return an alternative value if an expression is NULL:

SELECT ProductName, UnitPrice * (UnitsInStock + IFNULL(UnitsOnOrder, 0))
FROM Products;

or we can use the function, like this:

SELECT ProductName, UnitPrice * (UnitsInStock + COALESCE(UnitsOnOrder, 0))
FROM Products;

SQL Server

The SQL Server function lets you return an alternative value when an expression is NULL:

SELECT ProductName, UnitPrice * (UnitsInStock + ISNULL(UnitsOnOrder, 0))
FROM Products;

or we can use the function, like this:

SELECT ProductName, UnitPrice * (UnitsInStock + COALESCE(UnitsOnOrder, 0))
FROM Products;

MS Access

The MS Access function returns TRUE (-1) if the expression is a null value, otherwise FALSE (0):

SELECT ProductName, UnitPrice * (UnitsInStock + IIF(IsNull(UnitsOnOrder), 0, UnitsOnOrder))
FROM Products;

Oracle

The Oracle NVL() function achieves the same result:

SELECT ProductName, UnitPrice * (UnitsInStock + NVL(UnitsOnOrder, 0))
FROM Products;

or we can use the COALESCE() function, like this:

SELECT ProductName, UnitPrice * (UnitsInStock + COALESCE(UnitsOnOrder, 0))
FROM Products;

SQL Stored Procedures for SQL Server

What is a Stored Procedure?

A stored procedure is a prepared SQL code that you can save, so the code can be reused over and over again.

So if you have an SQL query that you write over and over again, save it as a stored procedure, and then just call it to execute it.

You can also pass parameters to a stored procedure, so that the stored procedure can act based on the parameter value(s) that is passed.

Stored Procedure Syntax

CREATE PROCEDURE procedure_name
AS
sql_statement
GO;

Execute a Stored Procedure

EXEC procedure_name;

Demo Database

Below is a selection from the "Customers" table in the Northwind sample database:

CustomerID	CustomerName	ContactName	Address	City	PostalCode	Country
1	Alfreds Futterkiste	Maria Anders	Obere Str. 57	Berlin	12209	Germany
2	Ana Trujillo Emparedados y helados	Ana Trujillo	Avda. de la Constitución 2222	México D.F.	05021	Mexico
3	Antonio Moreno Taquería	Antonio Moreno	Mataderos 2312	México D.F.	05023	Mexico
4	Around the Horn	Thomas Hardy	120 Hanover Sq.	London	WA1 1DP	UK
5	Berglunds snabbköp	Christina Berglund	Berguvsvägen 8	Luleå	S-958 22	Sweden

Stored Procedure Example

The following SQL statement creates a stored procedure named "SelectAllCustomers" that selects all records from the "Customers" table:

Example

CREATE PROCEDURE SelectAllCustomers
AS
SELECT * FROM Customers
GO;

Execute the stored procedure above as follows:

Example

EXEC SelectAllCustomers;

Stored Procedure With One Parameter

The following SQL statement creates a stored procedure that selects Customers from a particular City from the "Customers" table:

Example

CREATE PROCEDURE SelectAllCustomers @City nvarchar(30)
AS
SELECT * FROM Customers WHERE City = @City
GO;

Execute the stored procedure above as follows:

Example

EXEC SelectAllCustomers @City = 'London';

Stored Procedure With Multiple Parameters

Setting up multiple parameters is very easy. Just list each parameter and the data type separated by a comma as shown below.

The following SQL statement creates a stored procedure that selects Customers from a particular City with a particular PostalCode from the "Customers" table:

Example

CREATE PROCEDURE SelectAllCustomers @City nvarchar(30), @PostalCode nvarchar(10)
AS
SELECT * FROM Customers WHERE City = @City AND PostalCode = @PostalCode
GO;

Execute the stored procedure above as follows:

Example

EXEC SelectAllCustomers @City = 'London', @PostalCode = 'WA1 1DP';

SQL Comments

Comments are used to explain sections of SQL statements, or to prevent execution of SQL statements.

Note: The examples in this chapter will not work in Firefox and Microsoft Edge!

Comments are not supported in Microsoft Access databases. Firefox and Microsoft Edge are using Microsoft Access database in our examples.

Single Line Comments

Single line comments start with --.

Any text between -- and the end of the line will be ignored (will not be executed).

The following example uses a single-line comment as an explanation:

Example

--Select all:
SELECT * FROM Customers;

The following example uses a single-line comment to ignore the end of a line:

Example

SELECT * FROM Customers -- WHERE City='Berlin';

The following example uses a single-line comment to ignore a statement:

Example

--SELECT * FROM Customers;
SELECT * FROM Products;

Multi-line Comments

Multi-line comments start with /* and end with */.

Any text between /* and */ will be ignored.

The following example uses a multi-line comment as an explanation:

Example

/*Select all the columns
of all the records
in the Customers table:*/
SELECT * FROM Customers;

The following example uses a multi-line comment to ignore many statements:

Example

/*SELECT * FROM Customers;
SELECT * FROM Products;
SELECT * FROM Orders;
SELECT * FROM Categories;*/
SELECT * FROM Suppliers;

To ignore just a part of a statement, also use the /* */ comment.

The following example uses a comment to ignore part of a line:

Example

SELECT CustomerName, /*City,*/ Country FROM Customers;

The following example uses a comment to ignore part of a statement:

Example

SELECT * FROM Customers WHERE (CustomerName LIKE 'L%'
OR CustomerName LIKE 'R%' /*OR CustomerName LIKE 'S%'
OR CustomerName LIKE 'T%'*/ OR CustomerName LIKE 'W%')
AND Country='USA'
ORDER BY CustomerName;

SQL Operators

SQL Arithmetic Operators

Operator	Description	Example
+	Add
-	Subtract
*	Multiply
/	Divide
%	Modulo

SQL Bitwise Operators

Operator	Description
&	Bitwise AND
\|	Bitwise OR
^	Bitwise exclusive OR

SQL Comparison Operators

Operator	Description	Example
=	Equal to
>	Greater than
<	Less than
>=	Greater than or equal to
<=	Less than or equal to
<>	Not equal to

SQL Compound Operators

Operator	Description
+=	Add equals
-=	Subtract equals
*=	Multiply equals
/=	Divide equals
%=	Modulo equals
&=	Bitwise AND equals
^-=	Bitwise exclusive equals
\|*=	Bitwise OR equals

SQL Logical Operators

Operator	Description	Example
ALL	TRUE if all of the subquery values meet the condition
AND	TRUE if all the conditions separated by AND is TRUE
ANY	TRUE if any of the subquery values meet the condition
BETWEEN	TRUE if the operand is within the range of comparisons
EXISTS	TRUE if the subquery returns one or more records
IN	TRUE if the operand is equal to one of a list of expressions
LIKE	TRUE if the operand matches a pattern
NOT	Displays a record if the condition(s) is NOT TRUE
OR	TRUE if any of the conditions separated by OR is TRUE
SOME	TRUE if any of the subquery values meet the condition

The SQL CREATE DATABASE Statement

The CREATE DATABASE statement is used to create a new SQL database.

Syntax

CREATE DATABASE databasename;

CREATE DATABASE Example

The following SQL statement creates a database called "testDB":

Example

CREATE DATABASE testDB;

Tip: Make sure you have admin privilege before creating any database. Once a database is created, you can check it in the list of databases with the following SQL command: SHOW DATABASES;

The SQL DROP DATABASE Statement

The DROP DATABASE statement is used to drop an existing SQL database.

Syntax

DROP DATABASE databasename;

Note: Be careful before dropping a database. Deleting a database will result in loss of complete information stored in the database!

DROP DATABASE Example

The following SQL statement drops the existing database "testDB":

Example

DROP DATABASE testDB;

Tip: Make sure you have admin privilege before dropping any database. Once a database is dropped, you can check it in the list of databases with the following SQL command: SHOW DATABASES;

The SQL BACKUP DATABASE Statement

The BACKUP DATABASE statement is used in SQL Server to create a full back up of an existing SQL database.

Syntax

BACKUP DATABASE databasename
TO DISK = 'filepath';

The SQL BACKUP WITH DIFFERENTIAL Statement

A differential back up only backs up the parts of the database that have changed since the last full database backup.

Syntax

BACKUP DATABASE databasename
TO DISK = 'filepath'
WITH DIFFERENTIAL;

BACKUP DATABASE Example

The following SQL statement creates a full back up of the existing database "testDB" to the D disk:

Example

BACKUP DATABASE testDB
TO DISK = 'D:backupstestDB.bak';

Tip: Always back up the database to a different drive than the actual database. Then, if you get a disk crash, you will not lose your backup file along with the database.

BACKUP WITH DIFFERENTIAL Example

The following SQL statement creates a differential back up of the database "testDB":

Example

BACKUP DATABASE testDB
TO DISK = 'D:backupstestDB.bak'
WITH DIFFERENTIAL;

Tip: A differential back up reduces the back up time (since only the changes are backed up).

The SQL CREATE TABLE Statement

The CREATE TABLE statement is used to create a new table in a database.

Syntax

CREATE TABLE table_name (
    column1 datatype,
    column2 datatype,
    column3 datatype,
   ....
);

The column parameters specify the names of the columns of the table.

The datatype parameter specifies the type of data the column can hold (e.g. varchar, integer, date, etc.).

Tip: For an overview of the available data types, go to our complete .

SQL CREATE TABLE Example

The following example creates a table called "Persons" that contains five columns: PersonID, LastName, FirstName, Address, and City:

Example

CREATE TABLE Persons (
    PersonID int,
    LastName varchar(255),
    FirstName varchar(255),
    Address varchar(255),
    City varchar(255)
);

The PersonID column is of type int and will hold an integer.

The LastName, FirstName, Address, and City columns are of type varchar and will hold characters, and the maximum length for these fields is 255 characters.

The empty "Persons" table will now look like this:

PersonID	LastName	FirstName	Address	City

Tip: The empty "Persons" table can now be filled with data with the SQL statement.

Create Table Using Another Table

A copy of an existing table can also be created using CREATE TABLE.

The new table gets the same column definitions. All columns or specific columns can be selected.

If you create a new table using an existing table, the new table will be filled with the existing values from the old table.

Syntax

CREATE TABLE new_table_name AS
    SELECT column1, column2,...
    FROM existing_table_name
    WHERE ....;

The following SQL creates a new table called "TestTables" (which is a copy of the "Customers" table):

Example

CREATE TABLE TestTable AS
SELECT customername, contactname
FROM customers;

The SQL DROP TABLE Statement

The DROP TABLE statement is used to drop an existing table in a database.

Syntax

DROP TABLE table_name;

Note: Be careful before dropping a table. Deleting a table will result in loss of complete information stored in the table!

SQL DROP TABLE Example

The following SQL statement drops the existing table "Shippers":

Example

DROP TABLE Shippers;

SQL TRUNCATE TABLE

The TRUNCATE TABLE statement is used to delete the data inside a table, but not the table itself.

Syntax

TRUNCATE TABLE table_name;

SQL ALTER TABLE Statement

The ALTER TABLE statement is used to add, delete, or modify columns in an existing table.

The ALTER TABLE statement is also used to add and drop various constraints on an existing table.

ALTER TABLE - ADD Column

To add a column in a table, use the following syntax:

ALTER TABLE table_name
ADD column_name datatype;

The following SQL adds an "Email" column to the "Customers" table:

Example

ALTER TABLE Customers
ADD Email varchar(255);

ALTER TABLE - DROP COLUMN

To delete a column in a table, use the following syntax (notice that some database systems don't allow deleting a column):

ALTER TABLE table_name
DROP COLUMN column_name;

The following SQL deletes the "Email" column from the "Customers" table:

Example

ALTER TABLE Customers
DROP COLUMN Email;

ALTER TABLE - RENAME COLUMN

To rename a column in a table, use the following syntax:

ALTER TABLE table_name
RENAME COLUMN old_name to new_name;

ALTER TABLE - ALTER/MODIFY DATATYPE

To change the data type of a column in a table, use the following syntax:

SQL Server / MS Access:

ALTER TABLE table_name
ALTER COLUMN column_name datatype;

My SQL / Oracle (prior version 10G):

ALTER TABLE table_name
MODIFY COLUMN column_name datatype;

Oracle 10G and later:

ALTER TABLE table_name
MODIFY column_name datatype;

SQL ALTER TABLE Example

Look at the "Persons" table:

ID	LastName	FirstName	Address	City
1	Hansen	Ola	Timoteivn 10	Sandnes
2	Svendson	Tove	Borgvn 23	Sandnes
3	Pettersen	Kari	Storgt 20	Stavanger

Now we want to add a column named "DateOfBirth" in the "Persons" table.

We use the following SQL statement:

ALTER TABLE Persons
ADD DateOfBirth date;

Notice that the new column, "DateOfBirth", is of type date and is going to hold a date. The data type specifies what type of data the column can hold. For a complete reference of all the data types available in MS Access, MySQL, and SQL Server, go to our complete .

The "Persons" table will now look like this:

ID	LastName	FirstName	Address	City
1	Hansen	Ola	Timoteivn 10	Sandnes
2	Svendson	Tove	Borgvn 23	Sandnes
3	Pettersen	Kari	Storgt 20	Stavanger

Change Data Type Example

Now we want to change the data type of the column named "DateOfBirth" in the "Persons" table.

We use the following SQL statement:

ALTER TABLE Persons
ALTER COLUMN DateOfBirth year;

Notice that the "DateOfBirth" column is now of type year and is going to hold a year in a two- or four-digit format.

DROP COLUMN Example

Next, we want to delete the column named "DateOfBirth" in the "Persons" table.

We use the following SQL statement:

ALTER TABLE Persons
DROP COLUMN DateOfBirth;

The "Persons" table will now look like this:

ID	LastName	FirstName	Address	City
1	Hansen	Ola	Timoteivn 10	Sandnes
2	Svendson	Tove	Borgvn 23	Sandnes
3	Pettersen	Kari	Storgt 20	Stavanger

SQL Constraints

SQL constraints are used to specify rules for data in a table.

SQL Create Constraints

Constraints can be specified when the table is created with the CREATE TABLE statement, or after the table is created with the ALTER TABLE statement.

Syntax

CREATE TABLE table_name (
    column1 datatype constraint,
    column2 datatype constraint,
    column3 datatype constraint,
    ....
);

SQL Constraints

SQL constraints are used to specify rules for the data in a table.

Constraints are used to limit the type of data that can go into a table. This ensures the accuracy and reliability of the data in the table. If there is any violation between the constraint and the data action, the action is aborted.

Constraints can be column level or table level. Column level constraints apply to a column, and table level constraints apply to the whole table.

The following constraints are commonly used in SQL:

- Ensures that a column cannot have a NULL value
- Ensures that all values in a column are different
- A combination of a NOT NULL and UNIQUE. Uniquely identifies each row in a table
- Prevents actions that would destroy links between tables
- Ensures that the values in a column satisfies a specific condition
- Sets a default value for a column if no value is specified
- Used to create and retrieve data from the database very quickly

SQL NOT NULL Constraint

By default, a column can hold NULL values.

The NOT NULL constraint enforces a column to NOT accept NULL values.

This enforces a field to always contain a value, which means that you cannot insert a new record, or update a record without adding a value to this field.

SQL NOT NULL on CREATE TABLE

The following SQL ensures that the "ID", "LastName", and "FirstName" columns will NOT accept NULL values when the "Persons" table is created:

Example

CREATE TABLE Persons (
    ID int NOT NULL,
    LastName varchar(255) NOT NULL,
    FirstName varchar(255) NOT NULL,
    Age int
);

SQL NOT NULL on ALTER TABLE

To create a NOT NULL constraint on the "Age" column when the "Persons" table is already created, use the following SQL:

SQL Server / MS Access:

ALTER TABLE Persons
ALTER COLUMN Age int NOT NULL;

My SQL / Oracle (prior version 10G):

ALTER TABLE Persons
MODIFY COLUMN Age int NOT NULL;

Oracle 10G and later:

ALTER TABLE Persons
MODIFY Age int NOT NULL;

SQL UNIQUE Constraint

The UNIQUE constraint ensures that all values in a column are different.

Both the UNIQUE and PRIMARY KEY constraints provide a guarantee for uniqueness for a column or set of columns.

A PRIMARY KEY constraint automatically has a UNIQUE constraint.

However, you can have many UNIQUE constraints per table, but only one PRIMARY KEY constraint per table.

SQL UNIQUE Constraint on CREATE TABLE

The following SQL creates a UNIQUE constraint on the "ID" column when the "Persons" table is created:

SQL Server / Oracle / MS Access:

CREATE TABLE Persons (
    ID int NOT NULL UNIQUE,
    LastName varchar(255) NOT NULL,
    FirstName varchar(255),
    Age int
);

MySQL:

CREATE TABLE Persons (
    ID int NOT NULL,
    LastName varchar(255) NOT NULL,
    FirstName varchar(255),
    Age int,
    UNIQUE (ID)
);

To name a UNIQUE constraint, and to define a UNIQUE constraint on multiple columns, use the following SQL syntax:

MySQL / SQL Server / Oracle / MS Access:

CREATE TABLE Persons (
    ID int NOT NULL,
    LastName varchar(255) NOT NULL,
    FirstName varchar(255),
    Age int,
    CONSTRAINT UC_Person UNIQUE (ID,LastName)
);

SQL UNIQUE Constraint on ALTER TABLE

To create a UNIQUE constraint on the "ID" column when the table is already created, use the following SQL:

MySQL / SQL Server / Oracle / MS Access:

ALTER TABLE Persons
ADD UNIQUE (ID);

To name a UNIQUE constraint, and to define a UNIQUE constraint on multiple columns, use the following SQL syntax:

MySQL / SQL Server / Oracle / MS Access:

ALTER TABLE Persons
ADD CONSTRAINT UC_Person UNIQUE (ID,LastName);

DROP a UNIQUE Constraint

To drop a UNIQUE constraint, use the following SQL:

MySQL:

ALTER TABLE Persons
DROP INDEX UC_Person;

SQL Server / Oracle / MS Access:

ALTER TABLE Persons
DROP CONSTRAINT UC_Person;

SQL PRIMARY KEY Constraint

The PRIMARY KEY constraint uniquely identifies each record in a table.

Primary keys must contain UNIQUE values, and cannot contain NULL values.

A table can have only ONE primary key; and in the table, this primary key can consist of single or multiple columns (fields).

SQL PRIMARY KEY on CREATE TABLE

The following SQL creates a PRIMARY KEY on the "ID" column when the "Persons" table is created:

MySQL:

CREATE TABLE Persons (
    ID int NOT NULL,
    LastName varchar(255) NOT NULL,
    FirstName varchar(255),
    Age int,
    PRIMARY KEY (ID)
);

SQL Server / Oracle / MS Access:

CREATE TABLE Persons (
    ID int NOT NULL PRIMARY KEY,
    LastName varchar(255) NOT NULL,
    FirstName varchar(255),
    Age int
);

To allow naming of a PRIMARY KEY constraint, and for defining a PRIMARY KEY constraint on multiple columns, use the following SQL syntax:

MySQL / SQL Server / Oracle / MS Access:

CREATE TABLE Persons (
    ID int NOT NULL,
    LastName varchar(255) NOT NULL,
    FirstName varchar(255),
    Age int,
    CONSTRAINT PK_Person PRIMARY KEY (ID,LastName)
);

Note: In the example above there is only ONE PRIMARY KEY (PK_Person). However, the VALUE of the primary key is made up of TWO COLUMNS (ID + LastName).

SQL PRIMARY KEY on ALTER TABLE

To create a PRIMARY KEY constraint on the "ID" column when the table is already created, use the following SQL:

MySQL / SQL Server / Oracle / MS Access:

ALTER TABLE Persons
ADD PRIMARY KEY (ID);

To allow naming of a PRIMARY KEY constraint, and for defining a PRIMARY KEY constraint on multiple columns, use the following SQL syntax:

MySQL / SQL Server / Oracle / MS Access:

ALTER TABLE Persons
ADD CONSTRAINT PK_Person PRIMARY KEY (ID,LastName);

Note: If you use ALTER TABLE to add a primary key, the primary key column(s) must have been declared to not contain NULL values (when the table was first created).

DROP a PRIMARY KEY Constraint

To drop a PRIMARY KEY constraint, use the following SQL:

MySQL:

ALTER TABLE Persons
DROP PRIMARY KEY;

SQL Server / Oracle / MS Access:

ALTER TABLE Persons
DROP CONSTRAINT PK_Person;

SQL FOREIGN KEY Constraint

The FOREIGN KEY constraint is used to prevent actions that would destroy links between tables.

A FOREIGN KEY is a field (or collection of fields) in one table, that refers to the in another table.

The table with the foreign key is called the child table, and the table with the primary key is called the referenced or parent table.

Look at the following two tables:

Persons Table

PersonID	LastName	FirstName	Age
1	Hansen	Ola	30
2	Svendson	Tove	23
3	Pettersen	Kari	20

Orders Table

OrderID	OrderNumber	PersonID
1	77895	3
2	44678	3
3	22456	2
4	24562	1

Notice that the "PersonID" column in the "Orders" table points to the "PersonID" column in the "Persons" table.

The "PersonID" column in the "Persons" table is the PRIMARY KEY in the "Persons" table.

The "PersonID" column in the "Orders" table is a FOREIGN KEY in the "Orders" table.

The FOREIGN KEY constraint prevents invalid data from being inserted into the foreign key column, because it has to be one of the values contained in the parent table.

SQL FOREIGN KEY on CREATE TABLE

The following SQL creates a FOREIGN KEY on the "PersonID" column when the "Orders" table is created:

MySQL:

CREATE TABLE Orders (
    OrderID int NOT NULL,
    OrderNumber int NOT NULL,
    PersonID int,
    PRIMARY KEY (OrderID),
    FOREIGN KEY (PersonID) REFERENCES Persons(PersonID)
);

SQL Server / Oracle / MS Access:

CREATE TABLE Orders (
    OrderID int NOT NULL PRIMARY KEY,
    OrderNumber int NOT NULL,
    PersonID int FOREIGN KEY REFERENCES Persons(PersonID)
);

To allow naming of a FOREIGN KEY constraint, and for defining a FOREIGN KEY constraint on multiple columns, use the following SQL syntax:

MySQL / SQL Server / Oracle / MS Access:

CREATE TABLE Orders (
    OrderID int NOT NULL,
    OrderNumber int NOT NULL,
    PersonID int,
    PRIMARY KEY (OrderID),
    CONSTRAINT FK_PersonOrder FOREIGN KEY (PersonID)
    REFERENCES Persons(PersonID)
);

SQL FOREIGN KEY on ALTER TABLE

To create a FOREIGN KEY constraint on the "PersonID" column when the "Orders" table is already created, use the following SQL:

MySQL / SQL Server / Oracle / MS Access:

ALTER TABLE Orders
ADD FOREIGN KEY (PersonID) REFERENCES Persons(PersonID);

To allow naming of a FOREIGN KEY constraint, and for defining a FOREIGN KEY constraint on multiple columns, use the following SQL syntax:

MySQL / SQL Server / Oracle / MS Access:

ALTER TABLE Orders
ADD CONSTRAINT FK_PersonOrder
FOREIGN KEY (PersonID) REFERENCES Persons(PersonID);

DROP a FOREIGN KEY Constraint

To drop a FOREIGN KEY constraint, use the following SQL:

MySQL:

ALTER TABLE Orders
DROP FOREIGN KEY FK_PersonOrder;

SQL Server / Oracle / MS Access:

ALTER TABLE Orders
DROP CONSTRAINT FK_PersonOrder;

SQL CHECK Constraint

The CHECK constraint is used to limit the value range that can be placed in a column.

If you define a CHECK constraint on a column it will allow only certain values for this column.

If you define a CHECK constraint on a table it can limit the values in certain columns based on values in other columns in the row.

SQL CHECK on CREATE TABLE

The following SQL creates a CHECK constraint on the "Age" column when the "Persons" table is created. The CHECK constraint ensures that the age of a person must be 18, or older:

MySQL:

CREATE TABLE Persons (
    ID int NOT NULL,
    LastName varchar(255) NOT NULL,
    FirstName varchar(255),
    Age int,
    CHECK (Age>=18)
);

SQL Server / Oracle / MS Access:

CREATE TABLE Persons (
    ID int NOT NULL,
    LastName varchar(255) NOT NULL,
    FirstName varchar(255),
    Age int CHECK (Age>=18)
);

To allow naming of a CHECK constraint, and for defining a CHECK constraint on multiple columns, use the following SQL syntax:

MySQL / SQL Server / Oracle / MS Access:

CREATE TABLE Persons (
    ID int NOT NULL,
    LastName varchar(255) NOT NULL,
    FirstName varchar(255),
    Age int,
    City varchar(255),
    CONSTRAINT CHK_Person CHECK (Age>=18 AND City='Sandnes')
);

SQL CHECK on ALTER TABLE

To create a CHECK constraint on the "Age" column when the table is already created, use the following SQL:

MySQL / SQL Server / Oracle / MS Access:

ALTER TABLE Persons
ADD CHECK (Age>=18);

To allow naming of a CHECK constraint, and for defining a CHECK constraint on multiple columns, use the following SQL syntax:

MySQL / SQL Server / Oracle / MS Access:

ALTER TABLE Persons
ADD CONSTRAINT CHK_PersonAge CHECK (Age>=18 AND City='Sandnes');

DROP a CHECK Constraint

To drop a CHECK constraint, use the following SQL:

SQL Server / Oracle / MS Access:

ALTER TABLE Persons
DROP CONSTRAINT CHK_PersonAge;

MySQL:

ALTER TABLE Persons
DROP CHECK CHK_PersonAge;

SQL DEFAULT Constraint

The DEFAULT constraint is used to set a default value for a column.

The default value will be added to all new records, if no other value is specified.

SQL DEFAULT on CREATE TABLE

The following SQL sets a DEFAULT value for the "City" column when the "Persons" table is created:

My SQL / SQL Server / Oracle / MS Access:

CREATE TABLE Persons (
    ID int NOT NULL,
    LastName varchar(255) NOT NULL,
    FirstName varchar(255),
    Age int,
    City varchar(255) DEFAULT 'Sandnes'
);

The DEFAULT constraint can also be used to insert system values, by using functions like :

CREATE TABLE Orders (
    ID int NOT NULL,
    OrderNumber int NOT NULL,
    OrderDate date DEFAULT GETDATE()
);

SQL DEFAULT on ALTER TABLE

To create a DEFAULT constraint on the "City" column when the table is already created, use the following SQL:

MySQL:

ALTER TABLE Persons
ALTER City SET DEFAULT 'Sandnes';

SQL Server:

ALTER TABLE Persons
ADD CONSTRAINT df_City
DEFAULT 'Sandnes' FOR City;

MS Access:

ALTER TABLE Persons
ALTER COLUMN City SET DEFAULT 'Sandnes';

Oracle:

ALTER TABLE Persons
MODIFY City DEFAULT 'Sandnes';

DROP a DEFAULT Constraint

To drop a DEFAULT constraint, use the following SQL:

MySQL:

ALTER TABLE Persons
ALTER City DROP DEFAULT;

SQL Server / Oracle / MS Access:

ALTER TABLE Persons
ALTER COLUMN City DROP DEFAULT;

SQL Server:

ALTER TABLE Persons
ALTER COLUMN City DROP DEFAULT;

SQL CREATE INDEX Statement

The CREATE INDEX statement is used to create indexes in tables.

Indexes are used to retrieve data from the database more quickly than otherwise. The users cannot see the indexes, they are just used to speed up searches/queries.

Note: Updating a table with indexes takes more time than updating a table without (because the indexes also need an update). So, only create indexes on columns that will be frequently searched against.

CREATE INDEX Syntax

Creates an index on a table. Duplicate values are allowed:

CREATE INDEX index_name
ON table_name (column1, column2, ...);

CREATE UNIQUE INDEX Syntax

Creates a unique index on a table. Duplicate values are not allowed:

CREATE UNIQUE INDEX index_name
ON table_name (column1, column2, ...);

Note: The syntax for creating indexes varies among different databases. Therefore: Check the syntax for creating indexes in your database.

CREATE INDEX Example

The SQL statement below creates an index named "idx_lastname" on the "LastName" column in the "Persons" table:

CREATE INDEX idx_lastname
ON Persons (LastName);

If you want to create an index on a combination of columns, you can list the column names within the parentheses, separated by commas:

CREATE INDEX idx_pname
ON Persons (LastName, FirstName);

DROP INDEX Statement

The DROP INDEX statement is used to delete an index in a table.

MS Access:

DROP INDEX index_name ON table_name;

SQL Server:

DROP INDEX table_name.index_name;

DB2/Oracle:

DROP INDEX index_name;

MySQL:

ALTER TABLE table_name
DROP INDEX index_name;

AUTO INCREMENT Field

Auto-increment allows a unique number to be generated automatically when a new record is inserted into a table.

Often this is the primary key field that we would like to be created automatically every time a new record is inserted.

Syntax for MySQL

The following SQL statement defines the "Personid" column to be an auto-increment primary key field in the "Persons" table:

CREATE TABLE Persons (
    Personid int NOT NULL AUTO_INCREMENT,
    LastName varchar(255) NOT NULL,
    FirstName varchar(255),
    Age int,
    PRIMARY KEY (Personid)
);

MySQL uses the AUTO_INCREMENT keyword to perform an auto-increment feature.

By default, the starting value for AUTO_INCREMENT is 1, and it will increment by 1 for each new record.

To let the AUTO_INCREMENT sequence start with another value, use the following SQL statement:

ALTER TABLE Persons AUTO_INCREMENT=100;

To insert a new record into the "Persons" table, we will NOT have to specify a value for the "Personid" column (a unique value will be added automatically):

INSERT INTO Persons (FirstName,LastName)
VALUES ('Lars','Monsen');

The SQL statement above would insert a new record into the "Persons" table. The "Personid" column would be assigned a unique value. The "FirstName" column would be set to "Lars" and the "LastName" column would be set to "Monsen".

Syntax for SQL Server

The following SQL statement defines the "Personid" column to be an auto-increment primary key field in the "Persons" table:

CREATE TABLE Persons (
    Personid int IDENTITY(1,1) PRIMARY KEY,
    LastName varchar(255) NOT NULL,
    FirstName varchar(255),
    Age int
);

The MS SQL Server uses the IDENTITY keyword to perform an auto-increment feature.

In the example above, the starting value for IDENTITY is 1, and it will increment by 1 for each new record.

Tip: To specify that the "Personid" column should start at value 10 and increment by 5, change it to IDENTITY(10,5).

To insert a new record into the "Persons" table, we will NOT have to specify a value for the "Personid" column (a unique value will be added automatically):

INSERT INTO Persons (FirstName,LastName)
VALUES ('Lars','Monsen');

Syntax for Access

The following SQL statement defines the "Personid" column to be an auto-increment primary key field in the "Persons" table:

CREATE TABLE Persons (
    Personid AUTOINCREMENT PRIMARY KEY,
    LastName varchar(255) NOT NULL,
    FirstName varchar(255),
    Age int
);

The MS Access uses the AUTOINCREMENT keyword to perform an auto-increment feature.

By default, the starting value for AUTOINCREMENT is 1, and it will increment by 1 for each new record.

Tip: To specify that the "Personid" column should start at value 10 and increment by 5, change the autoincrement to AUTOINCREMENT(10,5).

To insert a new record into the "Persons" table, we will NOT have to specify a value for the "Personid" column (a unique value will be added automatically):

INSERT INTO Persons (FirstName,LastName)
VALUES ('Lars','Monsen');

Syntax for Oracle

In Oracle the code is a little bit more tricky.

You will have to create an auto-increment field with the sequence object (this object generates a number sequence).

Use the following CREATE SEQUENCE syntax:

CREATE SEQUENCE seq_person
MINVALUE 1
START WITH 1
INCREMENT BY 1
CACHE 10;

The code above creates a sequence object called seq_person, that starts with 1 and will increment by 1. It will also cache up to 10 values for performance. The cache option specifies how many sequence values will be stored in memory for faster access.

To insert a new record into the "Persons" table, we will have to use the nextval function (this function retrieves the next value from seq_person sequence):

INSERT INTO Persons (Personid,FirstName,LastName)
VALUES (seq_person.nextval,'Lars','Monsen');

The SQL statement above would insert a new record into the "Persons" table. The "Personid" column would be assigned the next number from the seq_person sequence. The "FirstName" column would be set to "Lars" and the "LastName" column would be set to "Monsen".

SQL Working With Dates

SQL Dates

The most difficult part when working with dates is to be sure that the format of the date you are trying to insert, matches the format of the date column in the database.

As long as your data contains only the date portion, your queries will work as expected. However, if a time portion is involved, it gets more complicated.

SQL Date Data Types

MySQL comes with the following data types for storing a date or a date/time value in the database:

DATE - format YYYY-MM-DD
DATETIME - format: YYYY-MM-DD HH:MI:SS
TIMESTAMP - format: YYYY-MM-DD HH:MI:SS
YEAR - format YYYY or YY

SQL Server comes with the following data types for storing a date or a date/time value in the database:

DATE - format YYYY-MM-DD
DATETIME - format: YYYY-MM-DD HH:MI:SS
SMALLDATETIME - format: YYYY-MM-DD HH:MI:SS
TIMESTAMP - format: a unique number

Note: The date types are chosen for a column when you create a new table in your database!

SQL Working with Dates

Look at the following table:

Orders Table

OrderId	ProductName	OrderDate
1	Geitost	2008-11-11
2	Camembert Pierrot	2008-11-09
3	Mozzarella di Giovanni	2008-11-11
4	Mascarpone Fabioli	2008-10-29

Now we want to select the records with an OrderDate of "2008-11-11" from the table above.

We use the following SELECT statement:

SELECT * FROM Orders WHERE OrderDate='2008-11-11'

The result-set will look like this:

OrderId	ProductName	OrderDate
1	Geitost	2008-11-11
3	Mozzarella di Giovanni	2008-11-11

Note: Two dates can easily be compared if there is no time component involved!

Now, assume that the "Orders" table looks like this (notice the added time-component in the "OrderDate" column):

OrderId	ProductName	OrderDate
1	Geitost	2008-11-11 13:23:44
2	Camembert Pierrot	2008-11-09 15:45:21
3	Mozzarella di Giovanni	2008-11-11 11:12:01
4	Mascarpone Fabioli	2008-10-29 14:56:59

If we use the same SELECT statement as above:

SELECT * FROM Orders WHERE OrderDate='2008-11-11'

we will get no result! This is because the query is looking only for dates with no time portion.

Tip: To keep your queries simple and easy to maintain, do not use time-components in your dates, unless you have to!

SQL Views

SQL CREATE VIEW Statement

In SQL, a view is a virtual table based on the result-set of an SQL statement.

A view contains rows and columns, just like a real table. The fields in a view are fields from one or more real tables in the database.

You can add SQL statements and functions to a view and present the data as if the data were coming from one single table.

A view is created with the CREATE VIEW statement.

CREATE VIEW Syntax

CREATE VIEW view_name AS
SELECT column1, column2, ...
FROM table_name
WHERE condition;

Note: A view always shows up-to-date data! The database engine recreates the view, every time a user queries it.

SQL CREATE VIEW Examples

The following SQL creates a view that shows all customers from Brazil:

Example

CREATE VIEW [Brazil Customers] AS
SELECT CustomerName, ContactName
FROM Customers
WHERE Country = 'Brazil';

We can query the view above as follows:

Example

SELECT * FROM [Brazil Customers];

The following SQL creates a view that selects every product in the "Products" table with a price higher than the average price:

Example

CREATE VIEW [Products Above Average Price] AS
SELECT ProductName, Price
FROM Products
WHERE Price > (SELECT AVG(Price) FROM Products);

We can query the view above as follows:

Example

SELECT * FROM [Products Above Average Price];

SQL Updating a View

A view can be updated with the CREATE OR REPLACE VIEW statement.

SQL CREATE OR REPLACE VIEW Syntax

CREATE OR REPLACE VIEW view_name AS
SELECT column1, column2, ...
FROM table_name
WHERE condition;

The following SQL adds the "City" column to the "Brazil Customers" view:

Example

CREATE OR REPLACE VIEW [Brazil Customers] AS
SELECT CustomerName, ContactName, City
FROM Customers
WHERE Country = 'Brazil';

SQL Dropping a View

A view is deleted with the DROP VIEW statement.

SQL DROP VIEW Syntax

DROP VIEW view_name;

The following SQL drops the "Brazil Customers" view:

Example

DROP VIEW [Brazil Customers];

SQL Injection

SQL injection is a code injection technique that might destroy your database.

SQL injection is one of the most common web hacking techniques.

SQL injection is the placement of malicious code in SQL statements, via web page input.

SQL in Web Pages

SQL injection usually occurs when you ask a user for input, like their username/userid, and instead of a name/id, the user gives you an SQL statement that you will unknowingly run on your database.

Look at the following example which creates a SELECT statement by adding a variable (txtUserId) to a select string. The variable is fetched from user input (getRequestString):

Example

txtUserId = getRequestString("UserId");
txtSQL = "SELECT * FROM Users WHERE UserId = " + txtUserId;

The rest of this chapter describes the potential dangers of using user input in SQL statements.

SQL Injection Based on 1=1 is Always True

Look at the example above again. The original purpose of the code was to create an SQL statement to select a user, with a given user id.

If there is nothing to prevent a user from entering "wrong" input, the user can enter some "smart" input like this:

UserId:

Then, the SQL statement will look like this:

SELECT * FROM Users WHERE UserId = 105 OR 1=1;

The SQL above is valid and will return ALL rows from the "Users" table, since OR 1=1 is always TRUE.

Does the example above look dangerous? What if the "Users" table contains names and passwords?

The SQL statement above is much the same as this:

SELECT UserId, Name, Password FROM Users WHERE UserId = 105 or 1=1;

A hacker might get access to all the user names and passwords in a database, by simply inserting 105 OR 1=1 into the input field.

SQL Injection Based on ""="" is Always True

Here is an example of a user login on a web site:

Username:

Password:

Example

uName = getRequestString("username");
uPass = getRequestString("userpassword");

sql = 'SELECT * FROM Users WHERE Name ="' + uName + '" AND Pass ="' + uPass + '"'

Result

SELECT * FROM Users WHERE Name ="John Doe" AND Pass ="myPass"

A hacker might get access to user names and passwords in a database by simply inserting " OR ""=" into the user name or password text box:

User Name:

Password:

The code at the server will create a valid SQL statement like this:

Result

SELECT * FROM Users WHERE Name ="" or ""="" AND Pass ="" or ""=""

The SQL above is valid and will return all rows from the "Users" table, since OR ""="" is always TRUE.

SQL Injection Based on Batched SQL Statements

Most databases support batched SQL statement.

A batch of SQL statements is a group of two or more SQL statements, separated by semicolons.

The SQL statement below will return all rows from the "Users" table, then delete the "Suppliers" table.

Example

SELECT * FROM Users; DROP TABLE Suppliers

Look at the following example:

Example

txtUserId = getRequestString("UserId");
txtSQL = "SELECT * FROM Users WHERE UserId = " + txtUserId;

And the following input:

User id:

The valid SQL statement would look like this:

Result

SELECT * FROM Users WHERE UserId = 105; DROP TABLE Suppliers;

Use SQL Parameters for Protection

To protect a web site from SQL injection, you can use SQL parameters.

SQL parameters are values that are added to an SQL query at execution time, in a controlled manner.

ASP.NET Razor Example

txtUserId = getRequestString("UserId");
txtSQL = "SELECT * FROM Users WHERE UserId = @0";
db.Execute(txtSQL,txtUserId);

Note that parameters are represented in the SQL statement by a @ marker.

The SQL engine checks each parameter to ensure that it is correct for its column and are treated literally, and not as part of the SQL to be executed.

Another Example

Examples

The following examples shows how to build parameterized queries in some common web languages.

SELECT STATEMENT IN ASP.NET:

txtUserId = getRequestString("UserId");
sql = "SELECT * FROM Customers WHERE CustomerId = @0";
command = new SqlCommand(sql);
command.Parameters.AddWithValue("@0",txtUserId);
command.ExecuteReader();

INSERT INTO STATEMENT IN ASP.NET:

txtNam = getRequestString("CustomerName");
txtAdd = getRequestString("Address");
txtCit = getRequestString("City");
txtSQL = "INSERT INTO Customers (CustomerName,Address,City) Values(@0,@1,@2)";
command = new SqlCommand(txtSQL);
command.Parameters.AddWithValue("@0",txtNam);
command.Parameters.AddWithValue("@1",txtAdd);
command.Parameters.AddWithValue("@2",txtCit);
command.ExecuteNonQuery();

INSERT INTO STATEMENT IN PHP:

$stmt = $dbh->prepare("INSERT INTO Customers (CustomerName,Address,City)
VALUES (:nam, :add, :cit)");
$stmt->bindParam(':nam', $txtNam);
$stmt->bindParam(':add', $txtAdd);
$stmt->bindParam(':cit', $txtCit);
$stmt->execute();

SQL Hosting

If you want your web site to be able to store and retrieve data from a database, your web server should have access to a database-system that uses the SQL language.

If your web server is hosted by an Internet Service Provider (ISP), you will have to look for SQL hosting plans.

The most common SQL hosting databases are MS SQL Server, Oracle, MySQL, and MS Access.

MS SQL Server

Microsoft's SQL Server is a popular database software for database-driven web sites with high traffic.

SQL Server is a very powerful, robust and full featured SQL database system.

Oracle

Oracle is also a popular database software for database-driven web sites with high traffic.

Oracle is a very powerful, robust and full featured SQL database system.

MySQL

MySQL is also a popular database software for web sites.

MySQL is a very powerful, robust and full featured SQL database system.

MySQL is an inexpensive alternative to the expensive Microsoft and Oracle solutions.

MS Access

When a web site requires only a simple database, Microsoft Access can be a solution.

MS Access is not well suited for very high-traffic, and not as powerful as MySQL, SQL Server, or Oracle.

SQL Data Types for MySQL, SQL Server, and MS Access

The data type of a column defines what value the column can hold: integer, character, money, date and time, binary, and so on.

SQL Data Types

Each column in a database table is required to have a name and a data type.

An SQL developer must decide what type of data that will be stored inside each column when creating a table. The data type is a guideline for SQL to understand what type of data is expected inside of each column, and it also identifies how SQL will interact with the stored data.

Note: Data types might have different names in different database. And even if the name is the same, the size and other details may be different! Always check the documentation!

MySQL Data Types (Version 8.0)

In MySQL there are three main data types: string, numeric, and date and time.

String Data Types

Data type	Description
CHAR(size)	A FIXED length string (can contain letters, numbers, and special characters). The size parameter specifies the column length in characters - can be from 0 to 255. Default is 1
VARCHAR(size)	A VARIABLE length string (can contain letters, numbers, and special characters). The size parameter specifies the maximum string length in characters - can be from 0 to 65535
BINARY(size)	Equal to CHAR(), but stores binary byte strings. The size parameter specifies the column length in bytes. Default is 1
VARBINARY(size)	Equal to VARCHAR(), but stores binary byte strings. The size parameter specifies the maximum column length in bytes.
TINYBLOB	For BLOBs (Binary Large Objects). Max length: 255 bytes
TINYTEXT	Holds a string with a maximum length of 255 characters
TEXT(size)	Holds a string with a maximum length of 65,535 bytes
BLOB(size)	For BLOBs (Binary Large Objects). Holds up to 65,535 bytes of data
MEDIUMTEXT	Holds a string with a maximum length of 16,777,215 characters
MEDIUMBLOB	For BLOBs (Binary Large Objects). Holds up to 16,777,215 bytes of data
LONGTEXT	Holds a string with a maximum length of 4,294,967,295 characters
LONGBLOB	For BLOBs (Binary Large Objects). Holds up to 4,294,967,295 bytes of data
ENUM(val1, val2, val3, ...)	A string object that can have only one value, chosen from a list of possible values. You can list up to 65535 values in an ENUM list. If a value is inserted that is not in the list, a blank value will be inserted. The values are sorted in the order you enter them
SET(val1, val2, val3, ...)	A string object that can have 0 or more values, chosen from a list of possible values. You can list up to 64 values in a SET list

Numeric Data Types

Data type	Description
BIT(size)	A bit-value type. The number of bits per value is specified in size. The size parameter can hold a value from 1 to 64. The default value for size is 1.
TINYINT(size)	A very small integer. Signed range is from -128 to 127. Unsigned range is from 0 to 255. The size parameter specifies the maximum display width (which is 255)
BOOL	Zero is considered as false, nonzero values are considered as true.
BOOLEAN	Equal to BOOL
SMALLINT(size)	A small integer. Signed range is from -32768 to 32767. Unsigned range is from 0 to 65535. The size parameter specifies the maximum display width (which is 255)
MEDIUMINT(size)	A medium integer. Signed range is from -8388608 to 8388607. Unsigned range is from 0 to 16777215. The size parameter specifies the maximum display width (which is 255)
INT(size)	A medium integer. Signed range is from -2147483648 to 2147483647. Unsigned range is from 0 to 4294967295. The size parameter specifies the maximum display width (which is 255)
INTEGER(size)	Equal to INT(size)
BIGINT(size)	A large integer. Signed range is from -9223372036854775808 to 9223372036854775807. Unsigned range is from 0 to 18446744073709551615. The size parameter specifies the maximum display width (which is 255)
FLOAT(size, d)	A floating point number. The total number of digits is specified in size. The number of digits after the decimal point is specified in the d parameter. This syntax is deprecated in MySQL 8.0.17, and it will be removed in future MySQL versions
FLOAT(p)	A floating point number. MySQL uses the p value to determine whether to use FLOAT or DOUBLE for the resulting data type. If p is from 0 to 24, the data type becomes FLOAT(). If p is from 25 to 53, the data type becomes DOUBLE()
DOUBLE(size, d)	A normal-size floating point number. The total number of digits is specified in size. The number of digits after the decimal point is specified in the d parameter
DOUBLE PRECISION(size, d)
DECIMAL(size, d)	An exact fixed-point number. The total number of digits is specified in size. The number of digits after the decimal point is specified in the d parameter. The maximum number for size is 65. The maximum number for d is 30. The default value for size is 10. The default value for d is 0.
DEC(size, d)	Equal to DECIMAL(size,d)

Note: All the numeric data types may have an extra option: UNSIGNED or ZEROFILL. If you add the UNSIGNED option, MySQL disallows negative values for the column. If you add the ZEROFILL option, MySQL automatically also adds the UNSIGNED attribute to the column.

Date and Time Data Types

Data type	Description
DATE	A date. Format: YYYY-MM-DD. The supported range is from '1000-01-01' to '9999-12-31'
DATETIME(fsp)	A date and time combination. Format: YYYY-MM-DD hh:mm:ss. The supported range is from '1000-01-01 00:00:00' to '9999-12-31 23:59:59'. Adding DEFAULT and ON UPDATE in the column definition to get automatic initialization and updating to the current date and time
TIMESTAMP(fsp)	A timestamp. TIMESTAMP values are stored as the number of seconds since the Unix epoch ('1970-01-01 00:00:00' UTC). Format: YYYY-MM-DD hh:mm:ss. The supported range is from '1970-01-01 00:00:01' UTC to '2038-01-09 03:14:07' UTC. Automatic initialization and updating to the current date and time can be specified using DEFAULT CURRENT_TIMESTAMP and ON UPDATE CURRENT_TIMESTAMP in the column definition
TIME(fsp)	A time. Format: hh:mm:ss. The supported range is from '-838:59:59' to '838:59:59'
YEAR	A year in four-digit format. Values allowed in four-digit format: 1901 to 2155, and 0000. MySQL 8.0 does not support year in two-digit format.

SQL Server Data Types

String Data Types

Data type	Description	Max size	Storage
char(n)	Fixed width character string	8,000 characters	Defined width
varchar(n)	Variable width character string	8,000 characters	2 bytes + number of chars
varchar(max)	Variable width character string	1,073,741,824 characters	2 bytes + number of chars
text	Variable width character string	2GB of text data	4 bytes + number of chars
nchar	Fixed width Unicode string	4,000 characters	Defined width x 2
nvarchar	Variable width Unicode string	4,000 characters
nvarchar(max)	Variable width Unicode string	536,870,912 characters
ntext	Variable width Unicode string	2GB of text data
binary(n)	Fixed width binary string	8,000 bytes
varbinary	Variable width binary string	8,000 bytes
varbinary(max)	Variable width binary string	2GB
image	Variable width binary string	2GB

Numeric Data Types

Data type	Description	Storage
bit	Integer that can be 0, 1, or NULL
tinyint	Allows whole numbers from 0 to 255	1 byte
smallint	Allows whole numbers between -32,768 and 32,767	2 bytes
int	Allows whole numbers between -2,147,483,648 and 2,147,483,647	4 bytes
bigint	Allows whole numbers between -9,223,372,036,854,775,808 and 9,223,372,036,854,775,807	8 bytes
decimal(p,s)	Fixed precision and scale numbers. Allows numbers from -10^38 +1 to 10^38 –1. The p parameter indicates the maximum total number of digits that can be stored (both to the left and to the right of the decimal point). p must be a value from 1 to 38. Default is 18. The s parameter indicates the maximum number of digits stored to the right of the decimal point. s must be a value from 0 to p. Default value is 0	5-17 bytes
numeric(p,s)	Fixed precision and scale numbers. Allows numbers from -10^38 +1 to 10^38 –1. The p parameter indicates the maximum total number of digits that can be stored (both to the left and to the right of the decimal point). p must be a value from 1 to 38. Default is 18. The s parameter indicates the maximum number of digits stored to the right of the decimal point. s must be a value from 0 to p. Default value is 0	5-17 bytes
smallmoney	Monetary data from -214,748.3648 to 214,748.3647	4 bytes
money	Monetary data from -922,337,203,685,477.5808 to 922,337,203,685,477.5807	8 bytes
float(n)	Floating precision number data from -1.79E + 308 to 1.79E + 308. The n parameter indicates whether the field should hold 4 or 8 bytes. float(24) holds a 4-byte field and float(53) holds an 8-byte field. Default value of n is 53.	4 or 8 bytes
real	Floating precision number data from -3.40E + 38 to 3.40E + 38	4 bytes

Date and Time Data Types

Data type	Description	Storage
datetime	From January 1, 1753 to December 31, 9999 with an accuracy of 3.33 milliseconds	8 bytes
datetime2	From January 1, 0001 to December 31, 9999 with an accuracy of 100 nanoseconds	6-8 bytes
smalldatetime	From January 1, 1900 to June 6, 2079 with an accuracy of 1 minute	4 bytes
date	Store a date only. From January 1, 0001 to December 31, 9999	3 bytes
time	Store a time only to an accuracy of 100 nanoseconds	3-5 bytes
datetimeoffset	The same as datetime2 with the addition of a time zone offset	8-10 bytes
timestamp	Stores a unique number that gets updated every time a row gets created or modified. The timestamp value is based upon an internal clock and does not correspond to real time. Each table may have only one timestamp variable

Other Data Types

Data type	Description
sql_variant	Stores up to 8,000 bytes of data of various data types, except text, ntext, and timestamp
uniqueidentifier	Stores a globally unique identifier (GUID)
xml	Stores XML formatted data. Maximum 2GB
cursor	Stores a reference to a cursor used for database operations
table	Stores a result-set for later processing

MS Access Data Types

Data type	Description	Storage
Text	Use for text or combinations of text and numbers. 255 characters maximum
Memo	Memo is used for larger amounts of text. Stores up to 65,536 characters. Note: You cannot sort a memo field. However, they are searchable
Byte	Allows whole numbers from 0 to 255	1 byte
Integer	Allows whole numbers between -32,768 and 32,767	2 bytes
Long	Allows whole numbers between -2,147,483,648 and 2,147,483,647	4 bytes
Single	Single precision floating-point. Will handle most decimals	4 bytes
Double	Double precision floating-point. Will handle most decimals	8 bytes
Currency	Use for currency. Holds up to 15 digits of whole dollars, plus 4 decimal places. Tip: You can choose which country's currency to use	8 bytes
AutoNumber	AutoNumber fields automatically give each record its own number, usually starting at 1	4 bytes
Date/Time	Use for dates and times	8 bytes
Yes/No	A logical field can be displayed as Yes/No, True/False, or On/Off. In code, use the constants True and False (equivalent to -1 and 0). Note: Null values are not allowed in Yes/No fields	1 bit
Ole Object	Can store pictures, audio, video, or other BLOBs (Binary Large Objects)	up to 1GB
Hyperlink	Contain links to other files, including web pages
Lookup Wizard	Let you type a list of options, which can then be chosen from a drop-down list	4 bytes

This SQL keywords reference contains the reserved words in SQL.

SQL Keywords

Keyword	Description
	Adds a column in an existing table
	Adds a constraint after a table is already created
	Returns true if all of the subquery values meet the condition
	Adds, deletes, or modifies columns in a table, or changes the data type of a column in a table
	Changes the data type of a column in a table
	Adds, deletes, or modifies columns in a table
	Only includes rows where both conditions is true
	Returns true if any of the subquery values meet the condition
	Renames a column or table with an alias
	Sorts the result set in ascending order
	Creates a back up of an existing database
	Selects values within a given range
	Creates different outputs based on conditions
	A constraint that limits the value that can be placed in a column
	Changes the data type of a column or deletes a column in a table
	Adds or deletes a constraint
	Creates a database, index, view, table, or procedure
	Creates a new SQL database
	Creates an index on a table (allows duplicate values)
	Updates a view
	Creates a new table in the database
	Creates a stored procedure
	Creates a unique index on a table (no duplicate values)
	Creates a view based on the result set of a SELECT statement
	Creates or deletes an SQL database
	A constraint that provides a default value for a column
	Deletes rows from a table
	Sorts the result set in descending order
	Selects only distinct (different) values
	Deletes a column, constraint, database, index, table, or view
	Deletes a column in a table
	Deletes a UNIQUE, PRIMARY KEY, FOREIGN KEY, or CHECK constraint
	Deletes an existing SQL database
	Deletes a DEFAULT constraint
	Deletes an index in a table
	Deletes an existing table in the database
	Deletes a view
	Executes a stored procedure
	Tests for the existence of any record in a subquery
	A constraint that is a key used to link two tables together
	Specifies which table to select or delete data from
	Returns all rows when there is a match in either left table or right table
	Groups the result set (used with aggregate functions: COUNT, MAX, MIN, SUM, AVG)
	Used instead of WHERE with aggregate functions
	Allows you to specify multiple values in a WHERE clause
	Creates or deletes an index in a table
	Returns rows that have matching values in both tables
	Inserts new rows in a table
	Copies data from one table into another table
	Tests for empty values
	Tests for non-empty values
	Joins tables
	Returns all rows from the left table, and the matching rows from the right table
	Searches for a specified pattern in a column
	Specifies the number of records to return in the result set
	Only includes rows where a condition is not true
	A constraint that enforces a column to not accept NULL values
	Includes rows where either condition is true
	Sorts the result set in ascending or descending order
	Returns all rows when there is a match in either left table or right table
	A constraint that uniquely identifies each record in a database table
	A stored procedure
	Returns all rows from the right table, and the matching rows from the left table
	Specifies the number of records to return in the result set
	Selects data from a database
	Selects only distinct (different) values
	Copies data from one table into a new table
	Specifies the number of records to return in the result set
	Specifies which columns and values that should be updated in a table
	Creates a table, or adds, deletes, or modifies columns in a table, or deletes a table or data inside a table
	Specifies the number of records to return in the result set
	Deletes the data inside a table, but not the table itself
	Combines the result set of two or more SELECT statements (only distinct values)
	Combines the result set of two or more SELECT statements (allows duplicate values)
	A constraint that ensures that all values in a column are unique
	Updates existing rows in a table
	Specifies the values of an INSERT INTO statement
	Creates, updates, or deletes a view
	Filters a result set to include only records that fulfill a specified condition

SQL ADD Keyword

ADD

The ADD command is used to add a column in an existing table.

The following SQL adds an "Email" column to the "Customers" table:

Example

ALTER TABLE Customers
ADD Email varchar(255);

SQL ADD CONSTRAINT Keyword

ADD CONSTRAINT

The ADD CONSTRAINT command is used to create a constraint after a table is already created.

The following SQL adds a constraint named "PK_Person" that is a PRIMARY KEY constraint on multiple columns (ID and LastName):

Example

ALTER TABLE Persons
ADD CONSTRAINT PK_Person PRIMARY KEY (ID,LastName);

SQL ALL Keyword

ALL

The ALL command returns true if all of the subquery values meet the condition.

The following SQL statement returns TRUE and lists the productnames if ALL the records in the OrderDetails table has quantity = 10:

Example

SELECT ProductName
FROM Products
WHERE ProductID = ALL (SELECT ProductID FROM OrderDetails WHERE Quantity = 10);

SQL ALTER Keyword

ALTER TABLE

The ALTER TABLE command adds, deletes, or modifies columns in a table.

The ALTER TABLE command also adds and deletes various constraints in a table.

The following SQL adds an "Email" column to the "Customers" table:

Example

ALTER TABLE Customers
ADD Email varchar(255);

The following SQL deletes the "Email" column from the "Customers" table:

Example

ALTER TABLE Customers
DROP COLUMN Email;

ALTER COLUMN

The ALTER COLUMN command is used to change the data type of a column in a table.

The following SQL changes the data type of the column named "BirthDate" in the "Employees" table to type year:

Example

ALTER TABLE Employees
ALTER COLUMN BirthDate year;

SQL ALTER COLUMN Keyword

ALTER COLUMN

The ALTER COLUMN command is used to change the data type of a column in a table.

The following SQL changes the data type of the column named "BirthDate" in the "Employees" table to type year:

Example

ALTER TABLE Employees
ALTER COLUMN BirthDate year;

SQL ALTER TABLE Keyword

ALTER TABLE

The ALTER TABLE command adds, deletes, or modifies columns in a table.

The ALTER TABLE command also adds and deletes various constraints in a table.

The following SQL adds an "Email" column to the "Customers" table:

Example

ALTER TABLE Customers
ADD Email varchar(255);

The following SQL deletes the "Email" column from the "Customers" table:

Example

ALTER TABLE Customers
DROP COLUMN Email;

SQL AND Keyword

AND

The AND command is used with WHERE to only include rows where both conditions is true.

The following SQL statement selects all fields from "Customers" where country is "Germany" AND city is "Berlin":

Example

SELECT * FROM Customers
WHERE Country='Germany' AND City='Berlin';

SQL ANY Keyword

ANY

The ANY command returns true if any of the subquery values meet the condition.

The following SQL statement returns TRUE and lists the productnames if it finds ANY records in the OrderDetails table where quantity = 10:

Example

SELECT ProductName
FROM Products
WHERE ProductID = ANY (SELECT ProductID FROM OrderDetails WHERE Quantity = 10);

The following SQL statement returns TRUE and lists the productnames if it finds ANY records in the OrderDetails table where quantity > 99:

Example

SELECT ProductName
FROM Products
WHERE ProductID = ANY (SELECT ProductID FROM OrderDetails WHERE Quantity > 99);

SQL AS Keyword

AS

The AS command is used to rename a column or table with an alias.

An alias only exists for the duration of the query.

Alias for Columns

The following SQL statement creates two aliases, one for the CustomerID column and one for the CustomerName column:

Example

SELECT CustomerID AS ID, CustomerName AS Customer
FROM Customers;

The following SQL statement creates two aliases. Notice that it requires double quotation marks or square brackets if the alias name contains spaces:

Example

SELECT CustomerName AS Customer, ContactName AS [Contact Person]
FROM Customers;

The following SQL statement creates an alias named "Address" that combine four columns (Address, PostalCode, City and Country):

Example

SELECT CustomerName, Address + ', ' + PostalCode + ' ' + City + ', ' + Country AS Address
FROM Customers;

Note: To get the SQL statement above to work in MySQL use the following:

SELECT CustomerName, CONCAT(Address,', ',PostalCode,', ',City,', ',Country) AS Address
FROM Customers;

Alias for Tables

Example

SELECT o.OrderID, o.OrderDate, c.CustomerName
FROM Customers AS c, Orders AS o
WHERE c.CustomerName="Around the Horn" AND c.CustomerID=o.CustomerID;

SQL ASC Keyword

ASC

The ASC command is used to sort the data returned in ascending order.

The following SQL statement selects all the columns from the "Customers" table, sorted by the "CustomerName" column:

Example

SELECT * FROM Customers
ORDER BY CustomerName ASC;

SQL BACKUP DATABASE Keyword

BACKUP DATABASE

The BACKUP DATABASE command is used in SQL Server to create a full back up of an existing SQL database.

The following SQL statement creates a full back up of the existing database "testDB" to the D disk:

Example

BACKUP DATABASE testDB
TO DISK = 'D:backupstestDB.bak';

Tip: Always back up the database to a different drive than the actual database. If you get a disk crash, you will not lose your backup file along with the database.

A differential back up only backs up the parts of the database that have changed since the last full database backup.

The following SQL statement creates a differential back up of the database "testDB":

Example

BACKUP DATABASE testDB
TO DISK = 'D:backupstestDB.bak'
WITH DIFFERENTIAL;

Tip: A differential back up reduces the back up time (since only the changes are backed up).

SQL BETWEEN Keyword

BETWEEN

The BETWEEN command is used to select values within a given range. The values can be numbers, text, or dates.

The BETWEEN command is inclusive: begin and end values are included.

The following SQL statement selects all products with a price BETWEEN 10 and 20:

Example

SELECT * FROM Products
WHERE Price BETWEEN 10 AND 20;

To display the products outside the range of the previous example, use NOT BETWEEN:

Example

SELECT * FROM Products
WHERE Price NOT BETWEEN 10 AND 20;

The following SQL statement selects all products with a ProductName BETWEEN 'Carnarvon Tigers' and 'Mozzarella di Giovanni':

Example

SELECT * FROM Products
WHERE ProductName BETWEEN 'Carnarvon Tigers' AND 'Mozzarella di Giovanni'
ORDER BY ProductName;

SQL CASE Keyword

CASE

The CASE command is used is to create different output based on conditions.

The following SQL goes through several conditions and returns a value when the specified condition is met:

Example

SELECT OrderID, Quantity,
CASE
    WHEN Quantity > 30 THEN 'The quantity is greater than 30'
    WHEN Quantity = 30 THEN 'The quantity is 30'
    ELSE 'The quantity is under 30'
END
FROM OrderDetails;

The following SQL will order the customers by City. However, if City is NULL, then order by Country:

Example

SELECT CustomerName, City, Country
FROM Customers
ORDER BY
(CASE
WHEN City IS NULL THEN Country
ELSE City
END);

SQL CHECK Keyword

CHECK

The CHECK constraint limits the value that can be placed in a column.

SQL CHECK on CREATE TABLE

The following SQL creates a CHECK constraint on the "Age" column when the "Persons" table is created. The CHECK constraint ensures that you can not have any person below 18 years:

MySQL:

CREATE TABLE Persons (
Age int,
CHECK (Age>=18)
);

SQL Server / Oracle / MS Access:

CREATE TABLE Persons (
Age int CHECK (Age>=18)
);

To allow naming of a CHECK constraint, and for defining a CHECK constraint on multiple columns, use the following SQL syntax:

MySQL / SQL Server / Oracle / MS Access:

CREATE TABLE Persons (
    Age int,
    City varchar(255),
    CONSTRAINT CHK_Person CHECK (Age>=18 AND City='Sandnes')
);

SQL CHECK on ALTER TABLE

To create a CHECK constraint on the "Age" column when the table is already created, use the following SQL:

MySQL / SQL Server / Oracle / MS Access:

ALTER TABLE Persons
ADD CHECK (Age>=18);

To allow naming of a CHECK constraint, and for defining a CHECK constraint on multiple columns, use the following SQL syntax:

MySQL / SQL Server / Oracle / MS Access:

ALTER TABLE Persons
ADD CONSTRAINT CHK_PersonAge CHECK (Age>=18 AND City='Sandnes');

DROP a CHECK Constraint

To drop a CHECK constraint, use the following SQL:

SQL Server / Oracle / MS Access:

ALTER TABLE Persons
DROP CONSTRAINT CHK_PersonAge;

MySQL:

ALTER TABLE Persons
DROP CHECK CHK_PersonAge;

SQL COLUMN Keyword

ALTER COLUMN

The ALTER COLUMN command is used to change the data type of a column in a table.

The following SQL changes the data type of the column named "BirthDate" in the "Employees" table to type year:

Example

ALTER TABLE Employees
ALTER COLUMN BirthDate year;

DROP COLUMN

The DROP COLUMN command is used to delete a column in an existing table.

The following SQL deletes the "ContactName" column from the "Customers" table:

Example

ALTER TABLE Customers
DROP COLUMN ContactName;

SQL CONSTRAINT Keyword

ADD CONSTRAINT

The ADD CONSTRAINT command is used to create a constraint after a table is already created.

The following SQL adds a constraint named "PK_Person" that is a PRIMARY KEY constraint on multiple columns (ID and LastName):

Example

ALTER TABLE Persons
ADD CONSTRAINT PK_Person PRIMARY KEY (ID,LastName);

DROP CONSTRAINT

The DROP CONSTRAINT command is used to delete a UNIQUE, PRIMARY KEY, FOREIGN KEY, or CHECK constraint.

DROP a UNIQUE Constraint

To drop a UNIQUE constraint, use the following SQL:

SQL Server / Oracle / MS Access:

ALTER TABLE Persons
DROP CONSTRAINT UC_Person;

MySQL:

ALTER TABLE Persons
DROP INDEX UC_Person;

DROP a PRIMARY KEY Constraint

To drop a PRIMARY KEY constraint, use the following SQL:

SQL Server / Oracle / MS Access:

ALTER TABLE Persons
DROP CONSTRAINT PK_Person;

MySQL:

ALTER TABLE Persons
DROP PRIMARY KEY;

DROP a FOREIGN KEY Constraint

To drop a FOREIGN KEY constraint, use the following SQL:

SQL Server / Oracle / MS Access:

ALTER TABLE Orders
DROP CONSTRAINT FK_PersonOrder;

MySQL:

ALTER TABLE Orders
DROP FOREIGN KEY FK_PersonOrder;

DROP a CHECK Constraint

To drop a CHECK constraint, use the following SQL:

SQL Server / Oracle / MS Access:

ALTER TABLE Persons
DROP CONSTRAINT CHK_PersonAge;

MySQL:

ALTER TABLE Persons
DROP CHECK CHK_PersonAge;

SQL CREATE Keyword

CREATE DATABASE

The CREATE DATABASE command is used is to create a new SQL database.

The following SQL creates a database called "testDB":

Example

CREATE DATABASE testDB;

Tip: Make sure you have admin privilege before creating any database. Once a database is created, you can check it in the list of databases with the following SQL command: SHOW DATABASES;

CREATE TABLE

The CREATE TABLE command creates a new table in the database.

The following SQL creates a table called "Persons" that contains five columns: PersonID, LastName, FirstName, Address, and City:

Example

CREATE TABLE Persons (
    PersonID int,
    LastName varchar(255),
    FirstName varchar(255),
    Address varchar(255),
    City varchar(255)
);

CREATE TABLE Using Another Table

The following SQL creates a new table called "TestTables" (which is a copy of two columns of the "Customers" table):

Example

CREATE TABLE TestTable AS
SELECT customername, contactname
FROM customers;

CREATE INDEX

The CREATE INDEX command is used to create indexes in tables (allows duplicate values).

Indexes are used to retrieve data from the database very fast. The users cannot see the indexes, they are just used to speed up searches/queries.

The following SQL creates an index named "idx_lastname" on the "LastName" column in the "Persons" table:

CREATE INDEX idx_lastname
ON Persons (LastName);

If you want to create an index on a combination of columns, you can list the column names within the parentheses, separated by commas:

CREATE INDEX idx_pname
ON Persons (LastName, FirstName);

Note: The syntax for creating indexes varies among different databases. Therefore: Check the syntax for creating indexes in your database.

CREATE UNIQUE INDEX

The CREATE UNIQUE INDEX command creates a unique index on a table (no duplicate values allowed)

The following SQL creates an index named "uidx_pid" on the "PersonID" column in the "Persons" table:

CREATE UNIQUE INDEX uidx_pid
ON Persons (PersonID);

CREATE VIEW

The CREATE VIEW command creates a view.

A view is a virtual table based on the result set of an SQL statement.

The following SQL creates a view that selects all customers from Brazil:

Example

CREATE VIEW [Brazil Customers] AS
SELECT CustomerName, ContactName
FROM Customers
WHERE Country = "Brazil";

CREATE OR REPLACE VIEW

The CREATE OR REPLACE VIEW command updates a view.

The following SQL adds the "City" column to the "Brazil Customers" view:

Example

CREATE OR REPLACE VIEW [Brazil Customers] AS
SELECT CustomerName, ContactName, City
FROM Customers
WHERE Country = "Brazil";

Query The View

We can query the view above as follows:

Example

SELECT * FROM [Brazil Customers];

CREATE PROCEDURE

The CREATE PROCEDURE command is used to create a stored procedure.

A stored procedure is a prepared SQL code that you can save, so the code can be reused over and over again.

The following SQL creates a stored procedure named "SelectAllCustomers" that selects all records from the "Customers" table:

Example

CREATE PROCEDURE SelectAllCustomers
AS
SELECT * FROM Customers
GO;

Execute the stored procedure above as follows:

Example

EXEC SelectAllCustomers;

SQL CREATE DATABASE Keyword

CREATE DATABASE

The CREATE DATABASE command is used is to create a new SQL database.

The following SQL creates a database called "testDB":

Example

CREATE DATABASE testDB;

Tip: Make sure you have admin privilege before creating any database. Once a database is created, you can check it in the list of databases with the following SQL command: SHOW DATABASES;

SQL CREATE INDEX Keyword

CREATE INDEX

The CREATE INDEX command is used to create indexes in tables (allows duplicate values).

Indexes are used to retrieve data from the database very fast. The users cannot see the indexes, they are just used to speed up searches/queries.

The following SQL creates an index named "idx_lastname" on the "LastName" column in the "Persons" table:

CREATE INDEX idx_lastname
ON Persons (LastName);

If you want to create an index on a combination of columns, you can list the column names within the parentheses, separated by commas:

CREATE INDEX idx_pname
ON Persons (LastName, FirstName);

Note: The syntax for creating indexes varies among different databases. Therefore: Check the syntax for creating indexes in your database.

SQL CREATE OR REPLACE VIEW Keyword

CREATE OR REPLACE VIEW

The CREATE OR REPLACE VIEW command updates a view.

The following SQL adds the "City" column to the "Brazil Customers" view:

Example

CREATE OR REPLACE VIEW [Brazil Customers] AS
SELECT CustomerName, ContactName, City
FROM Customers
WHERE Country = "Brazil";

Query The View

We can query the view above as follows:

Example

SELECT * FROM [Brazil Customers];

SQL CREATE TABLE Keyword

CREATE TABLE

The CREATE TABLE command creates a new table in the database.

The following SQL creates a table called "Persons" that contains five columns: PersonID, LastName, FirstName, Address, and City:

Example

CREATE TABLE Persons (
    PersonID int,
    LastName varchar(255),
    FirstName varchar(255),
    Address varchar(255),
    City varchar(255)
);

CREATE TABLE Using Another Table

The following SQL creates a new table called "TestTables" (which is a copy of two columns of the "Customers" table):

Example

CREATE TABLE TestTable AS
SELECT customername, contactname
FROM customers;

SQL CREATE PROCEDURE Keyword

CREATE PROCEDURE

The CREATE PROCEDURE command is used to create a stored procedure.

A stored procedure is a prepared SQL code that you can save, so the code can be reused over and over again.

The following SQL creates a stored procedure named "SelectAllCustomers" that selects all records from the "Customers" table:

Example

CREATE PROCEDURE SelectAllCustomers
AS
SELECT * FROM Customers
GO;

Execute the stored procedure above as follows:

Example

EXEC SelectAllCustomers;

SQL CREATE UNIQUE INDEX Keyword

CREATE UNIQUE INDEX

The CREATE UNIQUE INDEX command creates a unique index on a table (no duplicate values allowed)

Indexes are used to retrieve data from the database very fast. The users cannot see the indexes, they are just used to speed up searches/queries.

The following SQL creates an index named "uidx_pid" on the "PersonID" column in the "Persons" table:

CREATE UNIQUE INDEX uidx_pid
ON Persons (PersonID);

Note: The syntax for creating indexes varies among different databases. Therefore: Check the syntax for creating indexes in your database.

SQL CREATE VIEW Keyword

CREATE VIEW

The CREATE VIEW command creates a view.

A view is a virtual table based on the result set of an SQL statement.

The following SQL creates a view that selects all customers from Brazil:

Example

CREATE VIEW [Brazil Customers] AS
SELECT CustomerName, ContactName
FROM Customers
WHERE Country = "Brazil";

Query The View

We can query the view above as follows:

Example

SELECT * FROM [Brazil Customers];

SQL DATABASE Keyword

CREATE DATABASE

The CREATE DATABASE command is used is to create a new SQL database.

The following SQL creates a database called "testDB":

Example

CREATE DATABASE testDB;

Tip: Make sure you have admin privilege before creating any database. Once a database is created, you can check it in the list of databases with the following SQL command: SHOW DATABASES;

DROP DATABASE

The DROP DATABASE command is used is to delete an existing SQL database.

The following SQL drops a database named "testDB":

Example

DROP DATABASE testDB;

Note: Be careful before dropping a database. Deleting a database will result in loss of complete information stored in the database!

SQL DEFAULT Keyword

DEFAULT

The DEFAULT constraint provides a default value for a column.

The default value will be added to all new records if no other value is specified.

SQL DEFAULT on CREATE TABLE

The following SQL sets a DEFAULT value for the "City" column when the "Persons" table is created:

My SQL / SQL Server / Oracle / MS Access:

CREATE TABLE Persons (
City varchar(255) DEFAULT 'Sandnes'
);

The DEFAULT constraint can also be used to insert system values, by using functions like GETDATE():

CREATE TABLE Orders (
OrderDate date DEFAULT GETDATE()
);

SQL DEFAULT on ALTER TABLE

To create a DEFAULT constraint on the "City" column when the table is already created, use the following SQL:

MySQL:

ALTER TABLE Persons
ALTER City SET DEFAULT 'Sandnes';

SQL Server:

ALTER TABLE Persons
ADD CONSTRAINT df_City
DEFAULT 'Sandnes' FOR City;

MS Access:

ALTER TABLE Persons
ALTER COLUMN City SET DEFAULT 'Sandnes';

Oracle:

ALTER TABLE Persons
MODIFY City DEFAULT 'Sandnes';

DROP a DEFAULT Constraint

To drop a DEFAULT constraint, use the following SQL:

MySQL:

ALTER TABLE Persons
ALTER City DROP DEFAULT;

SQL Server / Oracle / MS Access:

ALTER TABLE Persons
ALTER COLUMN City DROP DEFAULT;

SQL DELETE Keyword

DELETE

The DELETE command is used to delete existing records in a table.

The following SQL statement deletes the customer "Alfreds Futterkiste" from the "Customers" table:

Example

DELETE FROM Customers WHERE CustomerName='Alfreds Futterkiste';

Note: Be careful when deleting records in a table! Notice the WHERE clause in the DELETE statement. The WHERE clause specifies which record(s) should be deleted. If you omit the WHERE clause, all records in the table will be deleted!

It is possible to delete all rows in a table without deleting the table. This means that the table structure, attributes, and indexes will be intact:

The following SQL statement deletes all rows in the "Customers" table, without deleting the table. This means that the table structure, attributes, and indexes will be intact:

Example

DELETE FROM Customers;

SQL DESC Keyword

DESC

The DESC command is used to sort the data returned in descending order.

The following SQL statement selects all the columns from the "Customers" table, sorted descending by the "CustomerName" column:

Example

SELECT * FROM Customers
ORDER BY CustomerName DESC;

SQL SELECT DISTINCT Keyword

SELECT DISTINCT

The SELECT DISTINCT command returns only distinct (different) values in the result set.

The following SQL statement selects only the DISTINCT values from the "Country" column in the "Customers" table:

Example

SELECT DISTINCT Country FROM Customers;

SQL DROP Keyword

DROP COLUMN

The DROP COLUMN command is used to delete a column in an existing table.

The following SQL deletes the "ContactName" column from the "Customers" table:

Example

ALTER TABLE Customers
DROP COLUMN ContactName;

DROP a UNIQUE Constraint

To drop a UNIQUE constraint, use the following SQL:

SQL Server / Oracle / MS Access:

ALTER TABLE Persons
DROP CONSTRAINT UC_Person;

MySQL:

ALTER TABLE Persons
DROP INDEX UC_Person;

DROP a PRIMARY KEY Constraint

To drop a PRIMARY KEY constraint, use the following SQL:

SQL Server / Oracle / MS Access:

ALTER TABLE Persons
DROP CONSTRAINT PK_Person;

MySQL:

ALTER TABLE Persons
DROP PRIMARY KEY;

DROP a FOREIGN KEY Constraint

To drop a FOREIGN KEY constraint, use the following SQL:

SQL Server / Oracle / MS Access:

ALTER TABLE Orders
DROP CONSTRAINT FK_PersonOrder;

MySQL:

ALTER TABLE Orders
DROP FOREIGN KEY FK_PersonOrder;

DROP a CHECK Constraint

To drop a CHECK constraint, use the following SQL:

SQL Server / Oracle / MS Access:

ALTER TABLE Persons
DROP CONSTRAINT CHK_PersonAge;

MySQL:

ALTER TABLE Persons
DROP CHECK CHK_PersonAge;

DROP DEFAULT

The DROP DEFAULT command is used to delete a DEFAULT constraint.

To drop a DEFAULT constraint, use the following SQL:

SQL Server / Oracle / MS Access:

ALTER TABLE Persons
ALTER COLUMN City DROP DEFAULT;

MySQL:

ALTER TABLE Persons
ALTER City DROP DEFAULT;

DROP INDEX

The DROP INDEX command is used to delete an index in a table.

MS Access:

DROP INDEX index_name ON table_name;

SQL Server:

DROP INDEX table_name.index_name;

DB2/Oracle:

DROP INDEX index_name;

MySQL:

ALTER TABLE table_name
DROP INDEX index_name;

DROP DATABASE

The DROP DATABASE command is used is to delete an existing SQL database.

The following SQL drops a database named "testDB":

Example

DROP DATABASE testDB;

Note: Be careful before dropping a database. Deleting a database will result in loss of complete information stored in the database!

DROP TABLE

The DROP TABLE command deletes a table in the database.

The following SQL deletes the table "Shippers":

Example

DROP TABLE Shippers;

Note: Be careful before deleting a table. Deleting a table results in loss of all information stored in the table!

DROP VIEW

The DROP VIEW command deletes a view.

The following SQL drops the "Brazil Customers" view:

Example

DROP VIEW [Brazil Customers];

SQL DROP COLUMN Keyword

DROP COLUMN

The DROP COLUMN command is used to delete a column in an existing table.

The following SQL deletes the "ContactName" column from the "Customers" table:

Example

ALTER TABLE Customers
DROP COLUMN ContactName;

SQL DROP CONSTRAINT Keyword

DROP CONSTRAINT

The DROP CONSTRAINT command is used to delete a UNIQUE, PRIMARY KEY, FOREIGN KEY, or CHECK constraint.

DROP a UNIQUE Constraint

To drop a UNIQUE constraint, use the following SQL:

SQL Server / Oracle / MS Access:

ALTER TABLE Persons
DROP CONSTRAINT UC_Person;

MySQL:

ALTER TABLE Persons
DROP INDEX UC_Person;

DROP a PRIMARY KEY Constraint

To drop a PRIMARY KEY constraint, use the following SQL:

SQL Server / Oracle / MS Access:

ALTER TABLE Persons
DROP CONSTRAINT PK_Person;

MySQL:

ALTER TABLE Persons
DROP PRIMARY KEY;

DROP a FOREIGN KEY Constraint

To drop a FOREIGN KEY constraint, use the following SQL:

SQL Server / Oracle / MS Access:

ALTER TABLE Orders
DROP CONSTRAINT FK_PersonOrder;

MySQL:

ALTER TABLE Orders
DROP FOREIGN KEY FK_PersonOrder;

DROP a CHECK Constraint

To drop a CHECK constraint, use the following SQL:

SQL Server / Oracle / MS Access:

ALTER TABLE Persons
DROP CONSTRAINT CHK_PersonAge;

MySQL:

ALTER TABLE Persons
DROP CHECK CHK_PersonAge;

SQL DROP DATABASE Keyword

DROP DATABASE

The DROP DATABASE command is used to delete an existing SQL database.

The following SQL drops a database named "testDB":

Example

DROP DATABASE testDB;

Note: Be careful before dropping a database. Deleting a database will result in loss of complete information stored in the database!

SQL DROP DEFAULT Keyword

DROP DEFAULT

The DROP DEFAULT command is used to delete a DEFAULT constraint.

To drop a DEFAULT constraint, use the following SQL:

SQL Server / Oracle / MS Access:

ALTER TABLE Persons
ALTER COLUMN City DROP DEFAULT;

MySQL:

ALTER TABLE Persons
ALTER City DROP DEFAULT;

SQL DROP INDEX Keyword

DROP INDEX

The DROP INDEX command is used to delete an index in a table.

MS Access:

DROP INDEX index_name ON table_name;

SQL Server:

DROP INDEX table_name.index_name;

DB2/Oracle:

DROP INDEX index_name;

MySQL:

ALTER TABLE table_name
DROP INDEX index_name;

SQL DROP TABLE and TRUNCATE TABLE Keywords

DROP TABLE

The DROP TABLE command deletes a table in the database.

The following SQL deletes the table "Shippers":

Example

DROP TABLE Shippers;

Note: Be careful before deleting a table. Deleting a table results in loss of all information stored in the table!

TRUNCATE TABLE

The TRUNCATE TABLE command deletes the data inside a table, but not the table itself.

The following SQL truncates the table "Categories":

Example

TRUNCATE TABLE Categories;

SQL DROP VIEW Keyword

DROP VIEW

The DROP VIEW command deletes a view.

The following SQL drops the "Brazil Customers" view:

Example

DROP VIEW [Brazil Customers];

SQL EXEC Keyword

EXEC

The EXEC command is used to execute a stored procedure.

The following SQL executes a stored procedure named "SelectAllCustomers":

Example

EXEC SelectAllCustomers;

SQL EXISTS Keyword

EXISTS

The EXISTS command tests for the existence of any record in a subquery, and returns true if the subquery returns one or more records.

The following SQL lists the suppliers with a product price less than 20:

Example

SELECT SupplierName
FROM Suppliers
WHERE EXISTS (SELECT ProductName FROM Products WHERE SupplierId = Suppliers.supplierId AND Price < 20);

The following SQL lists the suppliers with a product price equal to 22:

Example

SELECT SupplierName
FROM Suppliers
WHERE EXISTS (SELECT ProductName FROM Products WHERE SupplierId = Suppliers.supplierId AND Price = 22);

SQL FOREIGN KEY Keyword

FOREIGN KEY

The FOREIGN KEY constraint is a key used to link two tables together.

A FOREIGN KEY is a field (or collection of fields) in one table that refers to the PRIMARY KEY in another table.

SQL FOREIGN KEY on CREATE TABLE

The following SQL creates a FOREIGN KEY on the "PersonID" column when the "Orders" table is created:

MySQL:

CREATE TABLE Orders (
    OrderID int NOT NULL,
    OrderNumber int NOT NULL,
    PersonID int,
    PRIMARY KEY (OrderID),
    FOREIGN KEY (PersonID) REFERENCES Persons(PersonID)
);

SQL Server / Oracle / MS Access:

CREATE TABLE Orders (
    OrderID int NOT NULL PRIMARY KEY,
    OrderNumber int NOT NULL,
    PersonID int FOREIGN KEY REFERENCES Persons(PersonID)
);

To allow naming of a FOREIGN KEY constraint, and for defining a FOREIGN KEY constraint on multiple columns, use the following SQL syntax:

MySQL / SQL Server / Oracle / MS Access:

SQL FOREIGN KEY on ALTER TABLE

To create a FOREIGN KEY constraint on the "PersonID" column when the "Orders" table is already created, use the following SQL:

MySQL / SQL Server / Oracle / MS Access:

ALTER TABLE Orders
ADD FOREIGN KEY (PersonID) REFERENCES Persons(PersonID);

To allow naming of a FOREIGN KEY constraint, and for defining a FOREIGN KEY constraint on multiple columns, use the following SQL syntax:

MySQL / SQL Server / Oracle / MS Access:

ALTER TABLE Orders
ADD CONSTRAINT FK_PersonOrder
FOREIGN KEY (PersonID) REFERENCES Persons(PersonID);

DROP a FOREIGN KEY Constraint

To drop a FOREIGN KEY constraint, use the following SQL:

MySQL:

ALTER TABLE Orders
DROP FOREIGN KEY FK_PersonOrder;

SQL Server / Oracle / MS Access:

ALTER TABLE Orders
DROP CONSTRAINT FK_PersonOrder;

SQL FROM Keyword

FROM

The FROM command is used to specify which table to select or delete data from.

The following SQL statement selects the "CustomerName" and "City" columns from the "Customers" table:

Example

SELECT CustomerName, City FROM Customers;

The following SQL statement selects all the columns from the "Customers" table:

Example

SELECT * FROM Customers;

The following SQL statement deletes the customer "Alfreds Futterkiste" from the "Customers" table:

Example

DELETE FROM Customers
WHERE CustomerName='Alfreds Futterkiste';

SQL FULL OUTER JOIN Keyword

FULL OUTER JOIN

The FULL OUTER JOIN command returns all rows when there is a match in either left table or right table.

The following SQL statement selects all customers, and all orders:

SELECT Customers.CustomerName, Orders.OrderID
FROM Customers
FULL OUTER JOIN Orders ON Customers.CustomerID=Orders.CustomerID
ORDER BY Customers.CustomerName;

Note: The FULL OUTER JOIN keyword returns all the rows from the left table (Customers), and all the rows from the right table (Orders). If there are rows in "Customers" that do not have matches in "Orders", or if there are rows in "Orders" that do not have matches in "Customers", those rows will be listed as well.

SQL GROUP BY Keyword

GROUP BY

The GROUP BY command is used to group the result set (used with aggregate functions: COUNT, MAX, MIN, SUM, AVG).

The following SQL lists the number of customers in each country:

Example

SELECT COUNT(CustomerID), Country
FROM Customers
GROUP BY Country;

The following SQL lists the number of customers in each country, sorted high to low:

Example

SELECT COUNT(CustomerID), Country
FROM Customers
GROUP BY Country
ORDER BY COUNT(CustomerID) DESC;

SQL HAVING Keyword

HAVING

The HAVING command is used instead of WHERE with aggregate functions.

The following SQL lists the number of customers in each country. Only include countries with more than 5 customers:

Example

SELECT COUNT(CustomerID), Country
FROM Customers
GROUP BY Country
HAVING COUNT(CustomerID) > 5;

The following SQL lists the number of customers in each country, sorted high to low (Only include countries with more than 5 customers):

Example

SELECT COUNT(CustomerID), Country
FROM Customers
GROUP BY Country
HAVING COUNT(CustomerID) > 5
ORDER BY COUNT(CustomerID) DESC;

SQL IN Keyword

IN

The IN command allows you to specify multiple values in a WHERE clause.

The IN operator is a shorthand for multiple OR conditions.

The following SQL selects all customers that are located in "Germany", "France" and "UK":

Example

SELECT * FROM Customers
WHERE Country IN ('Germany', 'France', 'UK');

The following SQL selects all customers that are NOT located in "Germany", "France" or "UK":

Example

SELECT * FROM Customers
WHERE Country NOT IN ('Germany', 'France', 'UK');

The following SQL selects all customers that are from the same countries as the suppliers:

Example

SELECT * FROM Customers
WHERE Country IN (SELECT Country FROM Suppliers);

SQL INDEX Keyword

CREATE INDEX

The CREATE INDEX command is used to create indexes in tables (allows duplicate values).

Indexes are used to retrieve data from the database very fast. The users cannot see the indexes, they are just used to speed up searches/queries.

The following SQL creates an index named "idx_lastname" on the "LastName" column in the "Persons" table:

CREATE INDEX idx_lastname
ON Persons (LastName);

If you want to create an index on a combination of columns, you can list the column names within the parentheses, separated by commas:

CREATE INDEX idx_pname
ON Persons (LastName, FirstName);

Note: The syntax for creating indexes varies among different databases. Therefore: Check the syntax for creating indexes in your database.

DROP INDEX

The DROP INDEX command is used to delete an index in a table.

MS Access:

DROP INDEX index_name ON table_name;

SQL Server:

DROP INDEX table_name.index_name;

DB2/Oracle:

DROP INDEX index_name;

MySQL:

ALTER TABLE table_name
DROP INDEX index_name;

SQL INNER JOIN Keyword

INNER JOIN

The INNER JOIN command returns rows that have matching values in both tables.

The following SQL selects all orders with customer information:

Example

SELECT Orders.OrderID, Customers.CustomerName
FROM Orders
INNER JOIN Customers ON Orders.CustomerID = Customers.CustomerID;

Note: The INNER JOIN keyword selects all rows from both tables as long as there is a match between the columns. If there are records in the "Orders" table that do not have matches in "Customers", these orders will not be shown!

The following SQL statement selects all orders with customer and shipper information:

Example

SQL INSERT INTO Keyword

INSERT INTO

The INSERT INTO command is used to insert new rows in a table.

The following SQL inserts a new record in the "Customers" table:

Example

INSERT INTO Customers (CustomerName, ContactName, Address, City, PostalCode, Country)
VALUES ('Cardinal', 'Tom B. Erichsen', 'Skagen 21', 'Stavanger', '4006', 'Norway');

The following SQL will insert a new record, but only insert data in the "CustomerName", "City", and "Country" columns (CustomerID will be updated automatically):

Example

INSERT INTO Customers (CustomerName, City, Country)
VALUES ('Cardinal', 'Stavanger', 'Norway');

SQL INSERT INTO SELECT Keyword

INSERT INTO SELECT

The INSERT INTO SELECT command copies data from one table and inserts it into another table.

The following SQL copies "Suppliers" into "Customers" (the columns that are not filled with data, will contain NULL):

Example

INSERT INTO Customers (CustomerName, City, Country)
SELECT SupplierName, City, Country FROM Suppliers;

The following SQL copies "Suppliers" into "Customers" (fill all columns):

Example

INSERT INTO Customers (CustomerName, ContactName, Address, City, PostalCode, Country)
SELECT SupplierName, ContactName, Address, City, PostalCode, Country FROM Suppliers;

The following SQL copies only the German suppliers into "Customers":

Example

INSERT INTO Customers (CustomerName, City, Country)
SELECT SupplierName, City, Country FROM Suppliers
WHERE Country='Germany';

SQL IS NULL Keyword

IS NULL

The IS NULL command is used to test for empty values (NULL values).

The following SQL lists all customers with a NULL value in the "Address" field:

Example

SELECT CustomerName, ContactName, Address
FROM Customers
WHERE Address IS NULL;

Note: A NULL value is different from a zero value or a field that contains spaces. A field with a NULL value is one that has been left blank during record creation!

Tip: Always use IS NULL to look for NULL values.

SQL IS NOT NULL Keyword

IS NOT NULL

The IS NOT NULL command is used to test for non-empty values (NOT NULL values).

The following SQL lists all customers with a value in the "Address" field:

Example

SELECT CustomerName, ContactName, Address
FROM Customers
WHERE Address IS NOT NULL;

SQL JOIN Keyword

INNER JOIN

The INNER JOIN command returns rows that have matching values in both tables.

The following SQL selects all orders with customer information:

Example

SELECT Orders.OrderID, Customers.CustomerName
FROM Orders
INNER JOIN Customers ON Orders.CustomerID = Customers.CustomerID;

The following SQL statement selects all orders with customer and shipper information:

Example

LEFT JOIN

The LEFT JOIN command returns all rows from the left table, and the matching rows from the right table. The result is NULL from the right side, if there is no match.

The following SQL will select all customers, and any orders they might have:

Example

SELECT Customers.CustomerName, Orders.OrderID
FROM Customers
LEFT JOIN Orders ON Customers.CustomerID = Orders.CustomerID
ORDER BY Customers.CustomerName;

Note: The LEFT JOIN keyword returns all records from the left table (Customers), even if there are no matches in the right table (Orders).

RIGHT JOIN

The RIGHT JOIN command returns all rows from the right table, and the matching records from the left table. The result is NULL from the left side, when there is no match.

The following SQL will return all employees, and any orders they might have placed:

Example

SELECT Orders.OrderID, Employees.LastName, Employees.FirstName
FROM Orders
RIGHT JOIN Employees ON Orders.EmployeeID = Employees.EmployeeID
ORDER BY Orders.OrderID;

Note: The RIGHT JOIN keyword returns all records from the right table (Employees), even if there are no matches in the left table (Orders).

FULL OUTER JOIN

The FULL OUTER JOIN command returns all rows when there is a match in either left table or right table.

The following SQL statement selects all customers, and all orders:

SELECT Customers.CustomerName, Orders.OrderID
FROM Customers
FULL OUTER JOIN Orders ON Customers.CustomerID=Orders.CustomerID
ORDER BY Customers.CustomerName;

SQL LEFT JOIN Keyword

LEFT JOIN

The LEFT JOIN command returns all rows from the left table, and the matching rows from the right table. The result is NULL from the right side, if there is no match.

The following SQL will select all customers, and any orders they might have:

Example

SELECT Customers.CustomerName, Orders.OrderID
FROM Customers
LEFT JOIN Orders ON Customers.CustomerID = Orders.CustomerID
ORDER BY Customers.CustomerName;

Note: The LEFT JOIN keyword returns all records from the left table (Customers), even if there are no matches in the right table (Orders).

SQL LIKE Keyword

LIKE

The LIKE command is used in a WHERE clause to search for a specified pattern in a column.

You can use two wildcards with LIKE:

% - Represents zero, one, or multiple characters
_ - Represents a single character (MS Access uses a question mark (?) instead)

The following SQL selects all customers with a CustomerName starting with "a":

Example

SELECT * FROM Customers
WHERE CustomerName LIKE 'a%';

The following SQL selects all customers with a CustomerName ending with "a":

Example

SELECT * FROM Customers
WHERE CustomerName LIKE '%a';

The following SQL selects all customers with a CustomerName that have "or" in any position:

Example

SELECT * FROM Customers
WHERE CustomerName LIKE '%or%';

The following SQL statement selects all customers with a CustomerName that starts with "a" and are at least 3 characters in length:

Example

SELECT * FROM Customers
WHERE CustomerName LIKE 'a__%';

SQL SELECT TOP, LIMIT and ROWNUM Keywords

SELECT TOP, LIMIT and ROWNUM

The LIMIT, SELECT TOP or ROWNUM command is used to specify the number of records to return.

Note: SQL Server uses SELECT TOP. MySQL uses LIMIT, and Oracle uses ROWNUM.

The following SQL statement selects the first three records from the "Customers" table (SQL SERVER):

Example

SELECT TOP 3 * FROM Customers;

The following SQL statement shows the equivalent example using the LIMIT clause (MySQL):

Example

SELECT * FROM Customers
LIMIT 3;

The following SQL statement shows the equivalent example using ROWNUM (Oracle):

Example

SELECT * FROM Customers
WHERE ROWNUM <= 3;

SQL NOT Keyword

NOT

The NOT command is used with WHERE to only include rows where a condition is not true.

The following SQL statement selects all fields from "Customers" where country is NOT "Germany":

Example

SELECT * FROM Customers
WHERE NOT Country='Germany';

SQL NOT NULL Keyword

NOT NULL

The NOT NULL constraint enforces a column to not accept NULL values, which means that you cannot insert or update a record without adding a value to this field.

The following SQL ensures that the "ID", "LastName", and "FirstName" columns will NOT accept NULL values:

Example

CREATE TABLE Persons (
    ID int NOT NULL,
    LastName varchar(255) NOT NULL,
    FirstName varchar(255) NOT NULL,
    Age int
);

The following SQL creates a NOT NULL constraint on the "Age" column when the "Persons" table is already created:

ALTER TABLE Persons
MODIFY Age int NOT NULL;

SQL OR Keyword

OR

The OR command is used with WHERE to include rows where either condition is true.

The following SQL statement selects all fields from "Customers" where city is "Berlin" OR city is "München":

Example

SELECT * FROM Customers
WHERE City='Berlin' OR City='München';

SQL ORDER BY Keyword

ORDER BY

The ORDER BY command is used to sort the result set in ascending or descending order.

The ORDER BY command sorts the result set in ascending order by default. To sort the records in descending order, use the DESC keyword.

The following SQL statement selects all the columns from the "Customers" table, sorted by the "CustomerName" column:

Example

SELECT * FROM Customers
ORDER BY CustomerName;

ASC

The ASC command is used to sort the data returned in ascending order.

The following SQL statement selects all the columns from the "Customers" table, sorted by the "CustomerName" column:

Example

SELECT * FROM Customers
ORDER BY CustomerName ASC;

DESC

The DESC command is used to sort the data returned in descending order.

The following SQL statement selects all the columns from the "Customers" table, sorted descending by the "CustomerName" column:

Example

SELECT * FROM Customers
ORDER BY CustomerName DESC;

SQL FULL OUTER JOIN Keyword

FULL OUTER JOIN

The FULL OUTER JOIN command returns all rows when there is a match in either left table or right table.

The following SQL statement selects all customers, and all orders:

SELECT Customers.CustomerName, Orders.OrderID
FROM Customers
FULL OUTER JOIN Orders ON Customers.CustomerID=Orders.CustomerID
ORDER BY Customers.CustomerName;

SQL PRIMARY KEY Keyword

PRIMARY KEY

The PRIMARY KEY constraint uniquely identifies each record in a table.

A table can have only one primary key, which may consist of one single or of multiple fields.

SQL PRIMARY KEY on CREATE TABLE

The following SQL creates a PRIMARY KEY on the "ID" column when the "Persons" table is created:

MySQL:

CREATE TABLE Persons (
    ID int NOT NULL,
    LastName varchar(255) NOT NULL,
    FirstName varchar(255),
    Age int,
    PRIMARY KEY (ID)
);

SQL Server / Oracle / MS Access:

CREATE TABLE Persons (
    ID int NOT NULL PRIMARY KEY,
    LastName varchar(255) NOT NULL,
    FirstName varchar(255),
    Age int
);

To allow naming of a PRIMARY KEY constraint, and for defining a PRIMARY KEY constraint on multiple columns, use the following SQL syntax:

MySQL / SQL Server / Oracle / MS Access:

CREATE TABLE Persons (
    ID int NOT NULL,
    LastName varchar(255) NOT NULL,
    FirstName varchar(255),
    Age int,
    CONSTRAINT PK_Person PRIMARY KEY (ID,LastName)
);

Note: In the example above there is only ONE PRIMARY KEY (PK_Person). However, the VALUE of the primary key is made up of TWO COLUMNS (ID + LastName).

SQL PRIMARY KEY on ALTER TABLE

To create a PRIMARY KEY constraint on the "ID" column when the table is already created, use the following SQL:

MySQL / SQL Server / Oracle / MS Access:

ALTER TABLE Persons
ADD PRIMARY KEY (ID);

To allow naming of a PRIMARY KEY constraint, and for defining a PRIMARY KEY constraint on multiple columns, use the following SQL syntax:

MySQL / SQL Server / Oracle / MS Access:

ALTER TABLE Persons
ADD CONSTRAINT PK_Person PRIMARY KEY (ID,LastName);

Note: If you use the ALTER TABLE statement to add a primary key, the primary key column(s) must already have been declared to not contain NULL values (when the table was first created).

DROP a PRIMARY KEY Constraint

To drop a PRIMARY KEY constraint, use the following SQL:

MySQL:

ALTER TABLE Persons
DROP PRIMARY KEY;

SQL Server / Oracle / MS Access:

ALTER TABLE Persons
DROP CONSTRAINT PK_Person;

SQL CREATE PROCEDURE Keyword

CREATE PROCEDURE

The CREATE PROCEDURE command is used to create a stored procedure.

A stored procedure is a prepared SQL code that you can save, so the code can be reused over and over again.

The following SQL creates a stored procedure named "SelectAllCustomers" that selects all records from the "Customers" table:

Example

CREATE PROCEDURE SelectAllCustomers
AS
SELECT * FROM Customers
GO;

Execute the stored procedure above as follows:

Example

EXEC SelectAllCustomers;

SQL RIGHT JOIN Keyword

RIGHT JOIN

The RIGHT JOIN command returns all rows from the right table, and the matching records from the left table. The result is NULL from the left side, when there is no match.

The following SQL will return all employees, and any orders they might have placed:

Example

SELECT Orders.OrderID, Employees.LastName, Employees.FirstName
FROM Orders
RIGHT JOIN Employees ON Orders.EmployeeID = Employees.EmployeeID
ORDER BY Orders.OrderID;

Note: The RIGHT JOIN keyword returns all records from the right table (Employees), even if there are no matches in the left table (Orders).

SQL SELECT TOP, LIMIT and ROWNUM Keywords

SELECT TOP, LIMIT and ROWNUM

The LIMIT, SELECT TOP or ROWNUM command is used to specify the number of records to return.

Note: SQL Server uses SELECT TOP. MySQL uses LIMIT, and Oracle uses ROWNUM.

The following SQL statement selects the first three records from the "Customers" table (SQL SERVER):

Example

SELECT TOP 3 * FROM Customers;

The following SQL statement shows the equivalent example using the LIMIT clause (MySQL):

Example

SELECT * FROM Customers
LIMIT 3;

The following SQL statement shows the equivalent example using ROWNUM (Oracle):

Example

SELECT * FROM Customers
WHERE ROWNUM <= 3;

SQL SELECT Keyword

SELECT

The SELECT command is used to select data from a database. The data returned is stored in a result table, called the result set.

The following SQL statement selects the "CustomerName" and "City" columns from the "Customers" table:

Example

SELECT CustomerName, City FROM Customers;

The following SQL statement selects all the columns from the "Customers" table:

Example

SELECT * FROM Customers;

SQL SELECT DISTINCT Keyword

SELECT DISTINCT

The SELECT DISTINCT command returns only distinct (different) values in the result set.

The following SQL statement selects only the DISTINCT values from the "Country" column in the "Customers" table:

Example

SELECT DISTINCT Country FROM Customers;

SQL SELECT INTO Keyword

SELECT INTO

The SELECT INTO command copies data from one table and inserts it into a new table.

The following SQL statement creates a backup copy of Customers:

SELECT * INTO CustomersBackup2017
FROM Customers;

The following SQL statement uses the IN clause to copy the table into a new table in another database:

SELECT * INTO CustomersBackup2017 IN 'Backup.mdb'
FROM Customers;

The following SQL statement copies only a few columns into a new table:

SELECT CustomerName, ContactName INTO CustomersBackup2017
FROM Customers;

The following SQL statement copies only the German customers into a new table:

SELECT * INTO CustomersGermany
FROM Customers
WHERE Country = 'Germany';

The following SQL statement copies data from more than one table into a new table:

SELECT Customers.CustomerName, Orders.OrderID
INTO CustomersOrderBackup2017
FROM Customers
LEFT JOIN Orders ON Customers.CustomerID = Orders.CustomerID;

SQL SELECT TOP, LIMIT and ROWNUM Keywords

SELECT TOP, LIMIT and ROWNUM

The LIMIT, SELECT TOP or ROWNUM command is used to specify the number of records to return.

Note: SQL Server uses SELECT TOP. MySQL uses LIMIT, and Oracle uses ROWNUM.

The following SQL statement selects the first three records from the "Customers" table (SQL SERVER):

Example

SELECT TOP 3 * FROM Customers;

The following SQL statement shows the equivalent example using the LIMIT clause (MySQL):

Example

SELECT * FROM Customers
LIMIT 3;

The following SQL statement shows the equivalent example using ROWNUM (Oracle):

Example

SELECT * FROM Customers
WHERE ROWNUM <= 3;

SQL SET Keyword

SET

The SET command is used with UPDATE to specify which columns and values that should be updated in a table.

The following SQL updates the first customer (CustomerID = 1) with a new ContactName and a new City:

Example

UPDATE Customers
SET ContactName = 'Alfred Schmidt', City= 'Frankfurt'
WHERE CustomerID = 1;

The following SQL will update the "ContactName" field to "Juan" for all records where Country is "Mexico":

Example

UPDATE Customers
SET ContactName='Juan'
WHERE Country='Mexico';

Note: Be careful when updating records in a table! Notice the WHERE clause in the UPDATE statement. The WHERE clause specifies which record(s) that should be updated. If you omit the WHERE clause, all records in the table will be updated!

SQL TABLE Keyword

CREATE TABLE

The CREATE TABLE command creates a new table in the database.

The following SQL creates a table called "Persons" that contains five columns: PersonID, LastName, FirstName, Address, and City:

Example

CREATE TABLE Persons (
    PersonID int,
    LastName varchar(255),
    FirstName varchar(255),
    Address varchar(255),
    City varchar(255)
);

CREATE TABLE Using Another Table

A copy of an existing table can also be created using CREATE TABLE.

The following SQL creates a new table called "TestTables" (which is a copy of the "Customers" table):

Example

CREATE TABLE TestTable AS
SELECT customername, contactname
FROM customers;

ALTER TABLE

The ALTER TABLE command adds, deletes, or modifies columns in a table.

The ALTER TABLE command also adds and deletes various constraints in a table.

The following SQL adds an "Email" column to the "Customers" table:

Example

ALTER TABLE Customers
ADD Email varchar(255);

The following SQL deletes the "Email" column from the "Customers" table:

Example

ALTER TABLE Customers
DROP COLUMN Email;

DROP TABLE

The DROP TABLE command deletes a table in the database.

The following SQL deletes the table "Shippers":

Example

DROP TABLE Shippers;

Note: Be careful before deleting a table. Deleting a table results in loss of all information stored in the table!

TRUNCATE TABLE

The TRUNCATE TABLE command deletes the data inside a table, but not the table itself.

The following SQL truncates the table "Categories":

Example

TRUNCATE TABLE Categories;

SQL SELECT TOP, LIMIT and ROWNUM Keywords

SELECT TOP, LIMIT and ROWNUM

The LIMIT, SELECT TOP or ROWNUM command is used to specify the number of records to return.

Note: SQL Server uses SELECT TOP. MySQL uses LIMIT, and Oracle uses ROWNUM.

The following SQL statement selects the first three records from the "Customers" table (SQL SERVER):

Example

SELECT TOP 3 * FROM Customers;

The following SQL statement shows the equivalent example using the LIMIT clause (MySQL):

Example

SELECT * FROM Customers
LIMIT 3;

The following SQL statement shows the equivalent example using ROWNUM (Oracle):

Example

SELECT * FROM Customers
WHERE ROWNUM <= 3;

SQL DROP TABLE and TRUNCATE TABLE Keywords

DROP TABLE

The DROP TABLE command deletes a table in the database.

The following SQL deletes the table "Shippers":

Example

DROP TABLE Shippers;

Note: Be careful before deleting a table. Deleting a table results in loss of all information stored in the table!

TRUNCATE TABLE

The TRUNCATE TABLE command deletes the data inside a table, but not the table itself.

The following SQL truncates the table "Categories":

Example

TRUNCATE TABLE Categories;

SQL UNION Keyword

UNION

The UNION command combines the result set of two or more SELECT statements (only distinct values)

The following SQL statement returns the cities (only distinct values) from both the "Customers" and the "Suppliers" table:

Example

SELECT City FROM Customers
UNION
SELECT City FROM Suppliers
ORDER BY City;

SQL UNION ALL Keyword

UNION ALL

The UNION ALL command combines the result set of two or more SELECT statements (allows duplicate values).

The following SQL statement returns the cities (duplicate values also) from both the "Customers" and the "Suppliers" table:

Example

SELECT City FROM Customers
UNION ALL
SELECT City FROM Suppliers
ORDER BY City;

SQL UNIQUE Keyword

UNIQUE

The UNIQUE constraint ensures that all values in a column are unique.

SQL UNIQUE Constraint on CREATE TABLE

The following SQL creates a UNIQUE constraint on the "ID" column when the "Persons" table is created:

SQL Server / Oracle / MS Access:

CREATE TABLE Persons (
    ID int NOT NULL UNIQUE,
    LastName varchar(255) NOT NULL,
    FirstName varchar(255),
    Age int
);

MySQL:

CREATE TABLE Persons (
    ID int NOT NULL,
    LastName varchar(255) NOT NULL,
    FirstName varchar(255),
    Age int,
    UNIQUE (ID)
);

To name a UNIQUE constraint, and to define a UNIQUE constraint on multiple columns, use the following SQL syntax:

MySQL / SQL Server / Oracle / MS Access:

CREATE TABLE Persons (
    ID int NOT NULL,
    LastName varchar(255) NOT NULL,
    FirstName varchar(255),
    Age int,
    CONSTRAINT UC_Person UNIQUE (ID,LastName)
);

SQL UNIQUE Constraint on ALTER TABLE

To create a UNIQUE constraint on the "ID" column when the table is already created, use the following SQL:

MySQL / SQL Server / Oracle / MS Access:

ALTER TABLE Persons
ADD UNIQUE (ID);

To name a UNIQUE constraint, and to define a UNIQUE constraint on multiple columns, use the following SQL syntax:

MySQL / SQL Server / Oracle / MS Access:

ALTER TABLE Persons
ADD CONSTRAINT UC_Person UNIQUE (ID,LastName);

DROP a UNIQUE Constraint

To drop a UNIQUE constraint, use the following SQL:

MySQL:

ALTER TABLE Persons
DROP INDEX UC_Person;

SQL Server / Oracle / MS Access:

ALTER TABLE Persons
DROP CONSTRAINT UC_Person;

SQL UPDATE Keyword

UPDATE

The UPDATE command is used to update existing rows in a table.

The following SQL statement updates the first customer (CustomerID = 1) with a new contact person and a new city.

Example

UPDATE Customers
SET ContactName = 'Alfred Schmidt', City= 'Frankfurt'
WHERE CustomerID = 1;

The following SQL statement will update the contactname to "Juan" for all records where country is "Mexico":

Example

UPDATE Customers
SET ContactName='Juan'
WHERE Country='Mexico';

SQL VALUES Keyword

VALUES

The VALUES command specifies the values of an INSERT INTO statement.

The following SQL inserts a new record in the "Customers" table:

Example

INSERT INTO Customers (CustomerName, ContactName, Address, City, PostalCode, Country)
VALUES ('Cardinal', 'Tom B. Erichsen', 'Skagen 21', 'Stavanger', '4006', 'Norway');

The following SQL will insert a new record, but only insert data in the "CustomerName", "City", and "Country" columns (CustomerID will be updated automatically):

Example

INSERT INTO Customers (CustomerName, City, Country)
VALUES ('Cardinal', 'Stavanger', 'Norway');

SQL VIEW Keyword

CREATE VIEW

In SQL, a view is a virtual table based on the result set of an SQL statement.

The CREATE VIEW command creates a view.

The following SQL creates a view that selects all customers from Brazil:

Example

CREATE VIEW [Brazil Customers] AS
SELECT CustomerName, ContactName
FROM Customers
WHERE Country = "Brazil";

Query The View

We can query the view above as follows:

Example

SELECT * FROM [Brazil Customers];

CREATE OR REPLACE VIEW

The CREATE OR REPLACE VIEW command updates a view.

The following SQL adds the "City" column to the "Brazil Customers" view:

Example

CREATE OR REPLACE VIEW [Brazil Customers] AS
SELECT CustomerName, ContactName, City
FROM Customers
WHERE Country = "Brazil";

DROP VIEW

The DROP VIEW command deletes a view.

The following SQL drops the "Brazil Customers" view:

Example

DROP VIEW [Brazil Customers];

SQL WHERE Keyword

SELECT

The WHERE command filters a result set to include only records that fulfill a specified condition.

The following SQL statement selects all the customers from "Mexico" in the "Customers" table:

Example

SELECT * FROM Customers
WHERE Country='Mexico';

SQL requires single quotes around text values (most database systems will also allow double quotes).

However, numeric fields should not be enclosed in quotes:

Example

SELECT * FROM Customers
WHERE CustomerID=1;

Note: The WHERE clause is not only used in SELECT statement, it is also used in UPDATE, DELETE statement, etc.!

The following operators can be used in the WHERE clause:

Operator	Description
=	Equal
<>	Not equal. Note: In some versions of SQL this operator may be written as !=
>	Greater than
<	Less than
>=	Greater than or equal
<=	Less than or equal
BETWEEN	Between a certain range
LIKE	Search for a pattern
IN	To specify multiple possible values for a column

MySQL Functions

MySQL has many built-in functions.

This reference contains string, numeric, date, and some advanced functions in MySQL.

MySQL String Functions

Function	Description
	Returns the ASCII value for the specific character
	Returns the length of a string (in characters)
	Returns the length of a string (in characters)
	Adds two or more expressions together
	Adds two or more expressions together with a separator
	Returns the index position of a value in a list of values
	Returns the position of a string within a list of strings
	Formats a number to a format like "#,###,###.##", rounded to a specified number of decimal places
	Inserts a string within a string at the specified position and for a certain number of characters
	Returns the position of the first occurrence of a string in another string
	Converts a string to lower-case
	Extracts a number of characters from a string (starting from left)
	Returns the length of a string (in bytes)
	Returns the position of the first occurrence of a substring in a string
	Converts a string to lower-case
	Left-pads a string with another string, to a certain length
	Removes leading spaces from a string
	Extracts a substring from a string (starting at any position)
	Returns the position of the first occurrence of a substring in a string
	Repeats a string as many times as specified
	Replaces all occurrences of a substring within a string, with a new substring
	Reverses a string and returns the result
	Extracts a number of characters from a string (starting from right)
	Right-pads a string with another string, to a certain length
	Removes trailing spaces from a string
	Returns a string of the specified number of space characters
	Compares two strings
	Extracts a substring from a string (starting at any position)
	Extracts a substring from a string (starting at any position)
	Returns a substring of a string before a specified number of delimiter occurs
	Removes leading and trailing spaces from a string
	Converts a string to upper-case
	Converts a string to upper-case

MySQL Numeric Functions

Function	Description
	Returns the absolute value of a number
	Returns the arc cosine of a number
	Returns the arc sine of a number
	Returns the arc tangent of one or two numbers
	Returns the arc tangent of two numbers
	Returns the average value of an expression
	Returns the smallest integer value that is >= to a number
	Returns the smallest integer value that is >= to a number
	Returns the cosine of a number
	Returns the cotangent of a number
	Returns the number of records returned by a select query
	Converts a value in radians to degrees
	Used for integer division
	Returns e raised to the power of a specified number
	Returns the largest integer value that is <= to a number
	Returns the greatest value of the list of arguments
	Returns the smallest value of the list of arguments
	Returns the natural logarithm of a number
	Returns the natural logarithm of a number, or the logarithm of a number to a specified base
	Returns the natural logarithm of a number to base 10
	Returns the natural logarithm of a number to base 2
	Returns the maximum value in a set of values
	Returns the minimum value in a set of values
	Returns the remainder of a number divided by another number
	Returns the value of PI
	Returns the value of a number raised to the power of another number
	Returns the value of a number raised to the power of another number
	Converts a degree value into radians
	Returns a random number
	Rounds a number to a specified number of decimal places
	Returns the sign of a number
	Returns the sine of a number
	Returns the square root of a number
	Calculates the sum of a set of values
	Returns the tangent of a number
	Truncates a number to the specified number of decimal places

MySQL Date Functions

Function	Description
	Adds a time/date interval to a date and then returns the date
	Adds a time interval to a time/datetime and then returns the time/datetime
	Returns the current date
	Returns the current date
	Returns the current time
	Returns the current date and time
	Returns the current time
	Extracts the date part from a datetime expression
	Returns the number of days between two date values
	Adds a time/date interval to a date and then returns the date
	Formats a date
	Subtracts a time/date interval from a date and then returns the date
	Returns the day of the month for a given date
	Returns the weekday name for a given date
	Returns the day of the month for a given date
	Returns the weekday index for a given date
	Returns the day of the year for a given date
	Extracts a part from a given date
	Returns a date from a numeric datevalue
	Returns the hour part for a given date
	Extracts the last day of the month for a given date
	Returns the current date and time
	Returns the current date and time
	Creates and returns a date based on a year and a number of days value
	Creates and returns a time based on an hour, minute, and second value
	Returns the microsecond part of a time/datetime
	Returns the minute part of a time/datetime
	Returns the month part for a given date
	Returns the name of the month for a given date
	Returns the current date and time
	Adds a specified number of months to a period
	Returns the difference between two periods
	Returns the quarter of the year for a given date value
	Returns the seconds part of a time/datetime
	Returns a time value based on the specified seconds
	Returns a date based on a string and a format
	Subtracts a time/date interval from a date and then returns the date
	Subtracts a time interval from a datetime and then returns the time/datetime
	Returns the current date and time
	Extracts the time part from a given time/datetime
	Formats a time by a specified format
	Converts a time value into seconds
	Returns the difference between two time/datetime expressions
	Returns a datetime value based on a date or datetime value
	Returns the number of days between a date and date "0000-00-00"
	Returns the week number for a given date
	Returns the weekday number for a given date
	Returns the week number for a given date
	Returns the year part for a given date
	Returns the year and week number for a given date

MySQL Advanced Functions

Function	Description
	Returns a binary representation of a number
	Converts a value to a binary string
	Goes through conditions and return a value when the first condition is met
	Converts a value (of any type) into a specified datatype
	Returns the first non-null value in a list
	Returns the unique connection ID for the current connection
	Converts a number from one numeric base system to another
	Converts a value into the specified datatype or character set
	Returns the user name and host name for the MySQL account that the server used to authenticate the current client
	Returns the name of the current database
	Returns a value if a condition is TRUE, or another value if a condition is FALSE
	Return a specified value if the expression is NULL, otherwise return the expression
	Returns 1 or 0 depending on whether an expression is NULL
	Returns the AUTO_INCREMENT id of the last row that has been inserted or updated in a table
	Compares two expressions and returns NULL if they are equal. Otherwise, the first expression is returned
	Returns the current MySQL user name and host name
	Returns the current MySQL user name and host name
	Returns the current MySQL user name and host name
	Returns the current version of the MySQL database

Example

Return the ASCII value of the first character in "CustomerName":

SELECT ASCII(CustomerName) AS NumCodeOfFirstChar
FROM Customers;

Definition and Usage

The ASCII() function returns the ASCII value for the specific character.

Syntax

ASCII(character)

Parameter Values

Parameter	Description
character	Required. The character to return the ASCII value for. If more than one character is entered, it will only return the value for the first character

Technical Details

Works in:	From MySQL 4.0

Example

Return the length of the string:

SELECT CHAR_LENGTH("SQL Tutorial") AS LengthOfString;

Definition and Usage

The CHAR_LENGTH() function return the length of a string (in characters).

Note: This function is equal to the function.

Syntax

CHAR_LENGTH(string)

Parameter Values

Parameter	Description
string	Required. The string to count the length for

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return the length of the text in the "CustomerName" column:

SELECT CHAR_LENGTH(CustomerName) AS LengthOfName
FROM Customers;

Example

Return the length of the string:

SELECT CHARACTER_LENGTH("SQL Tutorial") AS LengthOfString;

Definition and Usage

The CHARACTER_LENGTH() function return the length of a string (in characters).

Note: This function is equal to the function.

Syntax

CHARACTER_LENGTH(string)

Parameter Values

Parameter	Description
string	Required. The string to count the length for

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return the length of the text in the "CustomerName" column:

SELECT CHARACTER_LENGTH(CustomerName) AS LengthOfName
FROM Customers;

Example

Add several strings together:

SELECT CONCAT("SQL ", "Tutorial ", "is ", "fun!") AS ConcatenatedString;

Definition and Usage

The CONCAT() function adds two or more expressions together.

Note: Also look at the function.

Syntax

CONCAT(expression1, expression2, expression3,...)

Parameter Values

Parameter	Description
expression1, expression2, expression3, etc.	Required. The expressions to add together. Note: If any of the expressions is a NULL value, it returns NULL

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Add three columns into one "Address" column:

SELECT CONCAT(Address, " ", PostalCode, " ", City) AS Address
FROM Customers;

Example

Add several expressions together, and add a "-" separator between them:

SELECT CONCAT_WS("-", "SQL", "Tutorial", "is", "fun!") AS ConcatenatedString;

Definition and Usage

The CONCAT_WS() function adds two or more expressions together with a separator.

Note: Also look at the function.

Syntax

CONCAT_WS(separator, expression1, expression2, expression3,...)

Parameter Values

Parameter	Description
separator	Required. The separator to add between each of the expressions. If separator is NULL, this function returns NULL
expression1, expression2, expression3, etc.	Required. The expressions to add together. An expression with a NULL value will be skipped

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Add three columns (and add a space between them) into one "Address" column:

SELECT CONCAT_WS(" ", Address, PostalCode, City) AS Address
FROM Customers;

Example

Return the index position of "q" in the string list:

SELECT FIELD("q", "s", "q", "l");

Definition and Usage

The FIELD() function returns the index position of a value in a list of values.

This function performs a case-insensitive search.

Note: If the specified value is not found in the list of values, this function will return 0. If value is NULL, this function will return 0.

Syntax

FIELD(value, val1, val2, val3, ...)

Parameter Values

Parameter	Description
value	Required. The value to search for in the list
val1, val2, val3, ....	Required. The list of values to search

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return the index position of "c" in the string list:

SELECT FIELD("c", "a", "b");

Example

Return the index position of "Q" in the string list:

SELECT FIELD("Q", "s", "q", "l");

Example

Return the index position of 5 in the numeric list:

SELECT FIELD(5, 0, 1, 2, 3, 4, 5);

Example

Search for "q" within the list of strings:

SELECT FIND_IN_SET("q", "s,q,l");

Definition and Usage

The FIND_IN_SET() function returns the position of a string within a list of strings.

Syntax

FIND_IN_SET(string, string_list)

Parameter Values

Parameter	Description
string	Required. The string to search for
string_list	Required. The list of string values to be searched (separated by commas)

Return Values

If string is not found in string_list, this function returns 0
If string or string_list is NULL, this function returns NULL
If string_list is an empty string (""), this function returns 0

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Search for "a" within the list of strings:

SELECT FIND_IN_SET("a", "s,q,l");

Example

Search for "q" within the list of strings (string list is NULL):

SELECT FIND_IN_SET("q", null);

Example

Format the number as "#,###,###.##" (and round with two decimal places):

SELECT FORMAT(250500.5634, 2);

Definition and Usage

The FORMAT() function formats a number to a format like "#,###,###.##", rounded to a specified number of decimal places, then it returns the result as a string.

Syntax

FORMAT(number, decimal_places)

Parameter Values

Parameter	Description
number	Required. The number to be formatted
decimal_places	Required. The number of decimal places for number. If this parameter is 0, this function returns a string with no decimal places

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Format the number as a format of "#,###,###.##" (and round with 0 decimal places):

SELECT FORMAT(250500.5634, 0);

Example

Insert the string "Example" into the string "W3Schools.com". Replace the first nine characters:

SELECT INSERT("W3Schools.com", 1, 9, "Example");

Definition and Usage

The INSERT() function inserts a string within a string at the specified position and for a certain number of characters.

Syntax

INSERT(string, position, number, string2)

Parameter Values

Parameter	Description
string	Required. The string that will be modified
position	Required. The position where to insert string2
number	Required. The number of characters to replace
string2	Required. The string to insert into string

Return Values

If position is outside the length of string, this function returns string
If number is higher than the length of the rest of the string, this function replaces string from position until the end of string

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Insert the string "no" into the string "W3Schools.com". Replace three characters, starting from position 11:

SELECT INSERT("W3Schools.com", 11, 3, "no");

Example

Search for "3" in string "W3Schools.com", and return position:

SELECT INSTR("W3Schools.com", "3") AS MatchPosition;

Definition and Usage

The INSTR() function returns the position of the first occurrence of a string in another string.

This function performs a case-insensitive search.

Syntax

INSTR(string1, string2)

Parameter Values

Parameter	Description
string1	Required. The string that will be searched
string2	Required. The string to search for in string1. If string2 is not found, this function returns 0

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Search for "COM" in string "W3Schools.com", and return position:

SELECT INSTR("W3Schools.com", "COM") AS MatchPosition;

Example

Search for "a" in CustomerName column, and return position:

SELECT INSTR(CustomerName, "a")
FROM Customers;

Example

Convert the text to lower-case:

SELECT LCASE("SQL Tutorial is FUN!");

Definition and Usage

The LCASE() function converts a string to lower-case.

Note: The function is a synonym for the LCASE() function.

Syntax

LCASE(text)

Parameter Values

Parameter	Description
text	Required. The string to convert

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Convert the text in "CustomerName" to lower-case:

SELECT LCASE(CustomerName) AS LowercaseCustomerName
FROM Customers;

Example

Extract 3 characters from a string (starting from left):

SELECT LEFT("SQL Tutorial", 3) AS ExtractString;

Definition and Usage

The LEFT() function extracts a number of characters from a string (starting from left).

Tip: Also look at the function.

Syntax

LEFT(string, number_of_chars)

Parameter Values

Parameter	Description
string	Required. The string to extract from
number_of_chars	Required. The number of characters to extract. If this parameter is larger than the number of characters in string, this function will return string

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Extract 5 characters from the text in the "CustomerName" column (starting from left):

SELECT LEFT(CustomerName, 5) AS ExtractString
FROM Customers;

Example

Return the length of the string, in bytes:

SELECT LENGTH("SQL Tutorial") AS LengthOfString;

Definition and Usage

The LENGTH() function returns the length of a string (in bytes).

Syntax

LENGTH(string)

Parameter Values

Parameter	Description
string	Required. The string to count the length for

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return the length of the text in the "CustomerName" column, in bytes:

SELECT LENGTH(CustomerName) AS LengthOfName
FROM Customers;

Example

Search for "3" in string "W3Schools.com", and return position:

SELECT LOCATE("3", "W3Schools.com") AS MatchPosition;

Definition and Usage

The LOCATE() function returns the position of the first occurrence of a substring in a string.

If the substring is not found within the original string, this function returns 0.

This function performs a case-insensitive search.

Note: This function is equal to the function.

Syntax

LOCATE(substring, string, start)

Parameter Values

Parameter	Description
substring	Required. The substring to search for in string
string	Required. The string that will be searched
start	Optional. The starting position for the search. Position 1 is default

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Search for "com" in string "W3Schools.com" (start at position 3), and return position:

SELECT LOCATE("com", "W3Schools.com", 3) AS MatchPosition;

Example

Search for "a" in CustomerName column, and return position:

SELECT LOCATE("a", CustomerName)
FROM Customers;

Example

Convert the text to lower-case:

SELECT LOWER("SQL Tutorial is FUN!");

Definition and Usage

The LOWER() function converts a string to lower-case.

Note: The function is equal to the LOWER() function.

Syntax

LOWER(text)

Parameter Values

Parameter	Description
text	Required. The string to convert

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Convert the text in "CustomerName" to lower-case:

SELECT LOWER(CustomerName) AS LowercaseCustomerName
FROM Customers;

Example

Left-pad the string with "ABC", to a total length of 20:

SELECT LPAD("SQL Tutorial", 20, "ABC");

Definition and Usage

The LPAD() function left-pads a string with another string, to a certain length.

Note: Also look at the function.

Syntax

LPAD(string, length, lpad_string)

Parameter Values

Parameter	Description
string	Required. The original string. If the length of the original string is larger than the length parameter, this function removes the overfloating characters from string
length	Required. The length of the string after it has been left-padded
lpad_string	Required. The string to left-pad to string

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Left-pad the text in "CustomerName" with "ABC", to a total length of 30:

SELECT LPAD(CustomerName, 30, "ABC") AS LeftPadCustomerName
FROM Customers;

Example

Remove leading spaces from a string:

SELECT LTRIM(" SQL Tutorial") AS LeftTrimmedString;

Definition and Usage

The LTRIM() function removes leading spaces from a string.

Syntax

LTRIM(string)

Parameter Values

Parameter	Description
string	Required. The string to remove leading spaces from

Technical Details

Works in:	From MySQL 4.0

Example

Extract a substring from a string (start at position 5, extract 3 characters):

SELECT MID("SQL Tutorial", 5, 3) AS ExtractString;

Definition and Usage

The MID() function extracts a substring from a string (starting at any position).

Note: The MID() and functions equals the function.

Syntax

MID(string, start, length)

Parameter Values

Parameter	Description
string	Required. The string to extract from
start	Required. The start position. Can be both a positive or negative number. If it is a positive number, this function extracts from the beginning of the string. If it is a negative number, this function extracts from the end of the string
length	Required. The number of characters to extract

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Extract a substring from the text in a column (start at position 2, extract 5 characters):

SELECT MID(CustomerName, 2, 5) AS ExtractString
FROM Customers;

Example

Extract a substring from a string (start from the end, at position -5, extract 5 characters):

SELECT MID("SQL Tutorial", -5, 5) AS ExtractString;

Example

Search for "3" in string "W3Schools.com", and return position:

SELECT POSITION("3" IN "W3Schools.com") AS MatchPosition;

Definition and Usage

The POSITION() function returns the position of the first occurrence of a substring in a string.

If the substring is not found within the original string, this function returns 0.

This function performs a case-insensitive search.

Note: The function is equal to the POSITION() function.

Syntax

POSITION(substring IN string)

Parameter Values

Parameter	Description
substring	Required. The substring to search for in string
string	Required. The original string that will be searched

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Search for "COM" in string "W3Schools.com", and return position:

SELECT POSITION("COM" IN "W3Schools.com") AS MatchPosition;

Example

Search for "a" in CustomerName column, and return position:

SELECT POSITION("a" IN CustomerName)
FROM Customers;

Example

Repeat a string 3 times:

SELECT REPEAT("SQL Tutorial", 3);

Definition and Usage

The REPEAT() function repeats a string as many times as specified.

Syntax

REPEAT(string, number)

Parameter Values

Parameter	Description
string	Required. The string to repeat
number	Required. The number of times to repeat the string

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Repeat the text in CustomerName 2 times:

SELECT REPEAT(CustomerName, 2)
FROM Customers;

Example

Repeat the string 0 times:

SELECT REPEAT("SQL Tutorial", 0);

Example

Replace "SQL" with "HTML":

SELECT REPLACE("SQL Tutorial", "SQL", "HTML");

Definition and Usage

The REPLACE() function replaces all occurrences of a substring within a string, with a new substring.

Note: This function performs a case-sensitive replacement.

Syntax

REPLACE(string, from_string, new_string)

Parameter Values

Parameter	Description
string	Required. The original string
from_string	Required. The substring to be replaced
new_string	Required. The new replacement substring

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Replace "X" with "M":

SELECT REPLACE("XYZ FGH XYZ", "X", "M");

Example

Replace "X" with "m":

SELECT REPLACE("XYZ FGH XYZ", "X", "m");

Example

Replace "x" with "m":

SELECT REPLACE("XYZ FGH XYZ", "x", "m");

Example

Reverse a string:

SELECT REVERSE("SQL Tutorial");

Definition and Usage

The REVERSE() function reverses a string and returns the result.

Syntax

REVERSE(string)

Parameter Values

Parameter	Description
string	Required. The string to reverse

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Reverse the text in CustomerName:

SELECT REVERSE(CustomerName)
FROM Customers;

Example

Extract 4 characters from a string (starting from right):

SELECT RIGHT("SQL Tutorial is cool", 4) AS ExtractString;

Definition and Usage

The RIGHT() function extracts a number of characters from a string (starting from right).

Tip: Also look at the function.

Syntax

RIGHT(string, number_of_chars)

Parameter Values

Parameter	Description
string	Required. The string to extract from
number_of_chars	Required. The number of characters to extract. If this parameter is larger than the number of characters in string, this function will return string

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Extract 5 characters from the text in the "CustomerName" column (starting from right):

SELECT RIGHT(CustomerName, 5) AS ExtractString
FROM Customers;

Example

Right-pad the string with "ABC", to a total length of 20:

SELECT RPAD("SQL Tutorial", 20, "ABC");

Definition and Usage

The RPAD() function right-pads a string with another string, to a certain length.

Note: Also look at the function.

Syntax

RPAD(string, length, rpad_string)

Parameter Values

Parameter	Description
string	Required. The original string. If the length of the original string is larger than the length parameter, this function removes the overfloating characters from string
length	Required. The length of the string after it has been right-padded
rpad_string	Required. The string to right-pad to string

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Right-pad the text in "CustomerName" with "ABC", to a total length of 30:

SELECT RPAD(CustomerName, 30, "ABC") AS RightPadCustomerName
FROM Customers;

Example

Remove trailing spaces from a string:

SELECT RTRIM("SQL Tutorial ") AS RightTrimmedString;

Definition and Usage

The RTRIM() function removes trailing spaces from a string.

Syntax

RTRIM(string)

Parameter Values

Parameter	Description
string	Required. The string to remove trailing spaces from

Technical Details

Works in:	From MySQL 4.0

Example

Return a string with 10 space characters:

SELECT SPACE(10);

Definition and Usage

The SPACE() function returns a string of the specified number of space characters.

Syntax

SPACE(number)

Parameter Values

Parameter	Description
number	Required. The number of space characters to return

Technical Details

Works in:	From MySQL 4.0

Example

Compare two strings:

SELECT STRCMP("SQL Tutorial", "SQL Tutorial");

Definition and Usage

The STRCMP() function compares two strings.

Syntax

STRCMP(string1, string2)

Parameter Values

Parameter	Description
string1, string2	Required. The two strings to be compared

Return Values

If string1 = string2, this function returns 0
If string1 < string2, this function returns -1
If string1 > string2, this function returns 1

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Compare two strings:

SELECT STRCMP("SQL Tutorial", "HTML Tutorial");

Example

Extract a substring from a string (start at position 5, extract 3 characters):

SELECT SUBSTR("SQL Tutorial", 5, 3) AS ExtractString;

Definition and Usage

The SUBSTR() function extracts a substring from a string (starting at any position).

Note: The SUBSTR() and functions equals to the function.

Syntax

SUBSTR(string, start, length)

OR:

SUBSTR(string FROM start FOR length)

Parameter Values

Parameter	Description
string	Required. The string to extract from
start	Required. The start position. Can be both a positive or negative number. If it is a positive number, this function extracts from the beginning of the string. If it is a negative number, this function extracts from the end of the string
length	Optional. The number of characters to extract. If omitted, the whole string will be returned (from the start position)

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Extract a substring from the text in a column (start at position 2, extract 5 characters):

SELECT SUBSTR(CustomerName, 2, 5) AS ExtractString
FROM Customers;

Example

Extract a substring from a string (start from the end, at position -5, extract 5 characters):

SELECT SUBSTR("SQL Tutorial", -5, 5) AS ExtractString;

Example

Extract a substring from a string (start at position 5, extract 3 characters):

SELECT SUBSTRING("SQL Tutorial", 5, 3) AS ExtractString;

Definition and Usage

The SUBSTRING() function extracts a substring from a string (starting at any position).

Note: The and functions equals to the SUBSTRING() function.

Syntax

SUBSTRING(string, start, length)

OR:

SUBSTRING(string FROM start FOR length)

Parameter Values

Parameter	Description
string	Required. The string to extract from
start	Required. The start position. Can be both a positive or negative number. If it is a positive number, this function extracts from the beginning of the string. If it is a negative number, this function extracts from the end of the string
length	Optional. The number of characters to extract. If omitted, the whole string will be returned (from the start position)

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Extract a substring from the text in a column (start at position 2, extract 5 characters):

SELECT SUBSTRING(CustomerName, 2, 5) AS ExtractString
FROM Customers;

Example

Extract a substring from a string (start from the end, at position -5, extract 5 characters):

SELECT SUBSTRING("SQL Tutorial", -5, 5) AS ExtractString;

Example

Return a substring of a string before a specified number of delimiter occurs:

SELECT SUBSTRING_INDEX("www.w3schools.com", ".", 1);

Definition and Usage

The SUBSTRING_INDEX() function returns a substring of a string before a specified number of delimiter occurs.

Syntax

SUBSTRING_INDEX(string, delimiter, number)

Parameter Values

Parameter	Description
string	Required. The original string
delimiter	Required. The delimiter to search for
number	Required. The number of times to search for the delimiter. Can be both a positive or negative number. If it is a positive number, this function returns all to the left of the delimiter. If it is a negative number, this function returns all to the right of the delimiter.

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return a substring of a string before a specified number of delimiter occurs:

SELECT SUBSTRING_INDEX("www.w3schools.com", ".", 2);

Example

Remove leading and trailing spaces from a string:

SELECT TRIM(' SQL Tutorial ') AS TrimmedString;

Definition and Usage

The TRIM() function removes leading and trailing spaces from a string.

Syntax

TRIM(string)

Parameter Values

Parameter	Description
string	Required. The string to remove leading and trailing spaces from

Technical Details

Works in:	From MySQL 4.0

Example

Convert the text to upper-case:

SELECT UCASE("SQL Tutorial is FUN!");

Definition and Usage

The UCASE() function converts a string to upper-case.

Note: This function is equal to the function.

Syntax

UCASE(text)

Parameter Values

Parameter	Description
text	Required. The string to convert

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Convert the text in "CustomerName" to upper-case:

SELECT UCASE(CustomerName) AS UppercaseCustomerName
FROM Customers;

Example

Convert the text to upper-case:

SELECT UPPER("SQL Tutorial is FUN!");

Definition and Usage

The UPPER() function converts a string to upper-case.

Note: This function is equal to the function.

Syntax

UPPER(text)

Parameter Values

Parameter	Description
text	Required. The string to convert

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Convert the text in "CustomerName" to upper-case:

SELECT UPPER(CustomerName) AS UppercaseCustomerName
FROM Customers;

Example

Return the absolute value of a number:

SELECT ABS(-243.5);

Definition and Usage

The ABS() function returns the absolute (positive) value of a number.

Syntax

ABS(number)

Parameter Values

Parameter	Description
number	Required. A numeric value

Technical Details

Works in:	From MySQL 4.0

Example

Return the arc cosine of a number:

SELECT ACOS(0.25);

Definition and Usage

The ACOS() function returns the arc cosine of a number.

The specified number must be between -1 to 1, otherwise this function returns NULL.

Syntax

ACOS(number)

Parameter Values

Parameter	Description
number	Required. A numeric value

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return the arc cosine of a number:

SELECT ACOS(-0.8);

Example

Return the arc sine of a number:

SELECT ASIN(0.25);

Definition and Usage

The ASIN() function returns the arc sine of a number.

The specified number must be between -1 to 1, otherwise this function returns NULL.

Syntax

ASIN(number)

Parameter Values

Parameter	Description
number	Required. A numeric value

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return the arc sine of a number:

SELECT ASIN(-0.8);

Example

Return the arc tangent of a number:

SELECT ATAN(2.5);

Definition and Usage

The ATAN() function returns the arc tangent of one or two numbers.

Syntax

ATAN(number)

OR:

ATAN(a, b)

Parameter Values

Parameter	Description
number	A numeric value
a, b	Two numeric values to calculate the arc tangent of

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return the arc tangent of two values:

SELECT ATAN(-0.8, 2);

Example

Return the arc tangent of two values:

SELECT ATAN2(0.50, 1);

Definition and Usage

The ATAN2() function returns the arc tangent of two numbers.

Syntax

ATAN2(a, b)

Parameter Values

Parameter	Description
a, b	Required. Two numeric values to calculate the arc tangent of

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return the arc tangent of two values:

SELECT ATAN2(-0.8, 2);

Example

Return the average value for the "Price" column in the "Products" table:

SELECT AVG(Price) AS AveragePrice FROM Products;

Definition and Usage

The AVG() function returns the average value of an expression.

Note: NULL values are ignored.

Syntax

AVG(expression)

Parameter Values

Parameter	Description
expression	Required. A numeric value (can be a field or a formula)

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Select the records that have a price above the average price:

SELECT * FROM Products
WHERE Price > (SELECT AVG(Price) FROM Products);

Example

Return the smallest integer value that is greater than or equal to 25.75:

SELECT CEIL(25.75);

Definition and Usage

The CEIL() function returns the smallest integer value that is bigger than or equal to a number.

Note: This function is equal to the function.

Syntax

CEIL(number)

Parameter Values

Parameter	Description
number	Required. A numeric value

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return the smallest integer value that is greater than or equal to 25:

SELECT CEIL(25);

Example

Return the smallest integer value that is greater than or equal to 25.75:

SELECT CEILING(25.75);

Definition and Usage

The CEILING() function returns the smallest integer value that is bigger than or equal to a number.

Note: This function is equal to the function.

Syntax

CEILING(number)

Parameter Values

Parameter	Description
number	Required. A numeric value

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return the smallest integer value that is greater than or equal to 25:

SELECT CEILING(25);

Example

Return the cosine of a number:

SELECT COS(2);

Definition and Usage

The COS() function returns the cosine of a number.

Syntax

COS(number)

Parameter Values

Parameter	Description
number	Required. A numeric value

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return the cosine of a number:

SELECT COS(PI());

Example

Return the cotangent of a number:

SELECT COT(6);

Definition and Usage

The COT() function returns the cotangent of a number.

Syntax

COT(number)

Parameter Values

Parameter	Description
number	Required. A numeric value. If number is 0, an error or NULL is returned

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return the cotangent of a number:

SELECT COT(-2);

Example

Return the number of products in the "Products" table:

SELECT COUNT(ProductID) AS NumberOfProducts FROM Products;

Definition and Usage

The COUNT() function returns the number of records returned by a select query.

Note: NULL values are not counted.

Syntax

COUNT(expression)

Parameter Values

Parameter	Description
expression	Required. A field or a string value

Technical Details

Works in:	From MySQL 4.0

Example

Convert the radian value into degrees:

SELECT DEGREES(1.5);

Definition and Usage

The DEGREES() function converts a value in radians to degrees.

Note: See also the and functions.

Syntax

DEGREES(number)

Parameter Values

Parameter	Description
number	Required. A numeric value

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Convert the radian value into degrees:

SELECT DEGREES(PI()*2);

Example

Integer division (10/5):

SELECT 10 DIV 5;

Definition and Usage

The DIV function is used for integer division (x is divided by y). An integer value is returned.

Syntax

x DIV y

Parameter Values

Parameter	Description
x	Required. A value that will be divided by y
y	Required. The divisor

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Integer division (8/3):

SELECT 8 DIV 3;

Example

Return e raised to the power of 1:

SELECT EXP(1);

Definition and Usage

The EXP() function returns e raised to the power of the specified number.

The constant e (2.718281...), is the base of natural logarithms.

Tip: Also look at the and functions.

Syntax

EXP(number)

Parameter Values

Parameter	Description
number	Required. The power number

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return e raised to the power of 2:

SELECT EXP(2);

Example

Return the largest integer value that is less than or equal to 25.75:

SELECT FLOOR(25.75);

Definition and Usage

The FLOOR() function returns the largest integer value that is smaller than or equal to a number.

Note: Also look at the , , , , and functions.

Syntax

FLOOR(number)

Parameter Values

Parameter	Description
number	Required. A numeric value

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return the largest integer value that is less than or equal to 25:

SELECT FLOOR(25);

Example

Return the greatest value of the list of arguments:

SELECT GREATEST(3, 12, 34, 8, 25);

Definition and Usage

The GREATEST() function returns the greatest value of the list of arguments.

Note: See also the function.

Syntax

GREATEST(arg1, arg2, arg3, ...)

Parameter Values

Parameter	Description
arg1, arg2, arg3, ...	Required. The list of arguments to be evaluated

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return the greatest value of the list of arguments:

SELECT GREATEST("w3Schools.com", "microsoft.com", "apple.com");

Example

Return the smallest value of the list of arguments:

SELECT LEAST(3, 12, 34, 8, 25);

Definition and Usage

The LEAST() function returns the smallest value of the list of arguments.

Note: See also the function.

Syntax

LEAST(arg1, arg2, arg3, ...)

Parameter Values

Parameter	Description
arg1, arg2, arg3, ...	Required. The list of arguments to be evaluated

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return the smallest value of the list of arguments:

SELECT LEAST("w3Schools.com", "microsoft.com", "apple.com");

Example

Return the natural logarithm of 2:

SELECT LN(2);

Definition and Usage

The LN() function returns the natural logarithm of a number.

Note: See also the and functions.

Syntax

LN(number)

Parameter Values

Parameter	Description
number	Required. A number. Must be greater than 0

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return the natural logarithm of 1:

SELECT LN(1);

Example

Return the natural logarithm of 2:

SELECT LOG(2);

Definition and Usage

The LOG() function returns the natural logarithm of a specified number, or the logarithm of the number to the specified base.

Note: See also the and functions.

Syntax

LOG(number)

OR:

LOG(base, number)

Parameter Values

Parameter	Description
number	Required. A number. Must be greater than 0
base	The base of number. Must be greater than 1

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return the natural logarithm of 4 to a specified base (2):

SELECT LOG(2, 4);

Example

Return the base-10 logarithm of 2:

SELECT LOG10(2);

Definition and Usage

The LOG10() function returns the natural logarithm of a number to base-10.

Note: See also the function.

Syntax

LOG10(number)

Parameter Values

Parameter	Description
number	A number greater than 0

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return the base-10 logarithm of 4.5:

SELECT LOG10(4.5);

Example

Return the base-2 logarithm of 6:

SELECT LOG2(6);

Definition and Usage

The LOG2() function returns the natural logarithm of a number to base-2.

Note: See also the function.

Syntax

LOG2(number)

Parameter Values

Parameter	Description
number	A number. Must be greater than 0

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return the base-2 logarithm of 64:

SELECT LOG2(64);

Example

Find the price of the most expensive product in the "Products" table:

SELECT MAX(Price) AS LargestPrice FROM Products;

Definition and Usage

The MAX() function returns the maximum value in a set of values.

Note: See also the function.

Syntax

MAX(expression)

Parameter Values

Parameter	Description
expression	Required. A numeric value (can be a field or a formula)

Technical Details

Works in:	From MySQL 4.0

Example

Find the price of the cheapest product in the "Products" table:

SELECT MIN(Price) AS SmallestPrice FROM Products;

Definition and Usage

The MIN() function returns the minimum value in a set of values.

Note: See also the function.

Syntax

MIN(expression)

Parameter Values

Parameter	Description
expression	Required. A numeric value (can be a field or a formula)

Technical Details

Works in:	From MySQL 4.0

Example

Return the remainder of 18/4:

SELECT MOD(18, 4);

Definition and Usage

The MOD() function returns the remainder of a number divided by another number.

Syntax

MOD(x, y)

OR:

x MOD y

OR:

x % y

Parameter Values

Parameter	Description
x	Required. A value that will be divided by y
y	Required. The divisor

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return the remainder of 18/4:

SELECT 18 MOD 4;

Example

Return the remainder of 18/4:

SELECT 18 % 4;

Example

Return the value of PI:

SELECT PI();

Definition and Usage

The PI() function returns the value of PI.

Note: See also the and functions.

Syntax

PI()

Technical Details

Works in:	From MySQL 4.0

Example

Return 4 raised to the second power:

SELECT POW(4, 2);

Definition and Usage

The POW() function returns the value of a number raised to the power of another number.

Note: This function is equal to the function.

Syntax

POW(x, y)

Parameter Values

Parameter	Description
x	Required. A number (the base)
y	Required. A number (the exponent)

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return 8 raised to the third power:

SELECT POW(8, 3);

Example

Return 4 raised to the second power:

SELECT POWER(4, 2);

Definition and Usage

The POWER() function returns the value of a number raised to the power of another number.

Note: This function is equal to the function.

Syntax

POWER(x, y)

Parameter Values

Parameter	Description
x	Required. A number (the base)
y	Required. A number (the exponent)

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return 8 raised to the third power:

SELECT POWER(8, 3);

Example

Convert a degree value into radians:

SELECT RADIANS(180);

Definition and Usage

The RADIANS() function converts a degree value into radians.

Note: See also the and functions.

Syntax

RADIANS(number)

Parameter Values

Parameter	Description
number	Required. A number in degrees

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Convert a degree value into radians:

SELECT RADIANS(-45);

Example

Return a random decimal number (no seed value - so it returns a completely random number >= 0 and <1):

SELECT RAND();

Definition and Usage

The RAND() function returns a random number between 0 (inclusive) and 1 (exclusive).

Syntax

RAND(seed)

Parameter Values

Parameter	Description
seed	Optional. If seed is specified, it returns a repeatable sequence of random numbers. If no seed is specified, it returns a completely random number

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return a random decimal number (with seed value of 6):

SELECT RAND(6);

Example

Return a random decimal number >= 5 and <10:

SELECT RAND()*(10-5)+5;

Example

Return a random number >= 5 and <=10:

SELECT FLOOR(RAND()*(10-5+1)+5);

Example

Round the number to 2 decimal places:

SELECT ROUND(135.375, 2);

Definition and Usage

The ROUND() function rounds a number to a specified number of decimal places.

Note: See also the , , , and functions.

Syntax

ROUND(number, decimals)

Parameter Values

Parameter	Description
number	Required. The number to be rounded
decimals	Optional. The number of decimal places to round number to. If omitted, it returns the integer (no decimals)

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Round the number to 0 decimal places:

SELECT ROUND(345.156, 0);

Example

Round the Price column (to 1 decimal) in the "Products" table:

SELECT ProductName, Price, ROUND(Price, 1) AS RoundedPrice
FROM Products;

Example

Return the sign of a number:

SELECT SIGN(255.5);

Definition and Usage

The SIGN() function returns the sign of a number.

This function will return one of the following:

If number > 0, it returns 1
If number = 0, it returns 0
If number < 0, it returns -1

Syntax

SIGN(number)

Parameter Values

Parameter	Description
number	Required. The number to return the sign for

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return the sign of a number:

SELECT SIGN(-12);

Example

Return the sine of a number:

SELECT SIN(2);

Definition and Usage

The SIN() function returns the sine of a number.

Syntax

SIN(number)

Parameter Values

Parameter	Description
number	Required. A numeric value

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return the sine of a number:

SELECT SIN(-1);

Example

Return the square root of a number:

SELECT SQRT(64);

Definition and Usage

The SQRT() function returns the square root of a number.

Syntax

SQRT(number)

Parameter Values

Parameter	Description
number	Required. A number to calculate the square root of. Must be greater than 0

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return the square root of a number:

SELECT SQRT(13);

Example

Return the sum of the "Quantity" field in the "OrderDetails" table:

SELECT SUM(Quantity) AS TotalItemsOrdered FROM OrderDetails;

Definition and Usage

The SUM() function calculates the sum of a set of values.

Note: NULL values are ignored.

Syntax

SUM(expression)

Parameter Values

Parameter	Description
expression	Required. A field or a formula

Technical Details

Works in:	From MySQL 4.0

Example

Return the tangent of a number:

SELECT TAN(1.75);

Definition and Usage

The TAN() function returns the tangent of a number.

Syntax

TAN(number)

Parameter Values

Parameter	Description
number	Required. A numeric value

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return the tangent of a number:

SELECT TAN(-3);

Example

Return a number truncated to 2 decimal places:

SELECT TRUNCATE(135.375, 2);

Definition and Usage

The TRUNCATE() function truncates a number to the specified number of decimal places.

Note: See also the , , , and functions.

Syntax

TRUNCATE(number, decimals)

Parameter Values

Parameter	Description
number	Required. The number to be truncated
decimals	Required. The number of decimal places to truncate to

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return a number truncated to 0 decimal places:

SELECT TRUNCATE(345.156, 0);

Example

Add 10 days to a date and return the date:

SELECT ADDDATE("2017-06-15", INTERVAL 10 DAY);

Definition and Usage

The ADDDATE() function adds a time/date interval to a date and then returns the date.

Syntax

ADDDATE(date, INTERVAL value addunit)

OR:

ADDDATE(date, days)

Parameter Values

Parameter	Description
date	Required. The date to be modified
days	Required. The number of days to add to date
value	Required. The value of the time/date interval to add. Both positive and negative values are allowed
addunit	Required. The type of interval to add. Can be one of the following values: MICROSECOND SECOND MINUTE HOUR DAY WEEK MONTH QUARTER YEAR SECOND_MICROSECOND MINUTE_MICROSECOND MINUTE_SECOND HOUR_MICROSECOND HOUR_SECOND HOUR_MINUTE DAY_MICROSECOND DAY_SECOND DAY_MINUTE DAY_HOUR YEAR_MONTH

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Add 15 minutes to a date and return the date:

SELECT ADDDATE("2017-06-15 09:34:21", INTERVAL 15 MINUTE);

Example

Subtract 3 hours to a date and return the date:

SELECT ADDDATE("2017-06-15 09:34:21", INTERVAL -3 HOUR);

Example

Subtract 2 months to a date and return the date:

SELECT ADDDATE("2017-06-15", INTERVAL -2 MONTH);

Example

Add 2 seconds to a time and return the datetime:

SELECT ADDTIME("2017-06-15 09:34:21", "2");

Definition and Usage

The ADDTIME() function adds a time interval to a time/datetime and then returns the time/datetime.

Syntax

ADDTIME(datetime, addtime)

Parameter Values

Parameter	Description
datetime	Required. The time/datetime to be modified
addtime	Required. The time interval to add to datetime. Both positive and negative values are allowed

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Add 5 seconds and 3 microseconds to a time and return the datetime:

SELECT ADDTIME("2017-06-15 09:34:21.000001", "5.000003");

Example

Add 2 hours, 10 minutes, 5 seconds, and 3 microseconds to a time and return the datetime:

SELECT ADDTIME("2017-06-15 09:34:21.000001", "2:10:5.000003");

Example

Add 5 days, 2 hours, 10 minutes, 5 seconds, and 3 microseconds to a time and return the datetime:

SELECT ADDTIME("2017-06-15 09:34:21.000001", "5 2:10:5.000003");

Example

Add 2 hours, 10 minutes, 5 seconds, and 3 microseconds to a time and return the time:

SELECT ADDTIME("09:34:21.000001", "2:10:5.000003");

Example

Return the current date:

SELECT CURDATE();

Definition and Usage

The CURDATE() function returns the current date.

Note: The date is returned as "YYYY-MM-DD" (string) or as YYYYMMDD (numeric).

Note: This function equals the function.

Syntax

CURDATE()

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return the current date + 1:

SELECT CURDATE() + 1;

Example

Return the current date:

SELECT CURRENT_DATE();

Definition and Usage

The CURRENT_DATE() function returns the current date.

Note: The date is returned as "YYYY-MM-DD" (string) or as YYYYMMDD (numeric).

Note: This function equals the function.

Syntax

CURRENT_DATE()

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return the current date + 1:

SELECT CURRENT_DATE() + 1;

Example

Return current time:

SELECT CURRENT_TIME();

Definition and Usage

The CURRENT_TIME() function returns the current time.

Note: The time is returned as "HH-MM-SS" (string) or as HHMMSS.uuuuuu (numeric).

Note: This function equals the function.

Syntax

CURRENT_TIME()

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return current time + 1:

SELECT CURRENT_TIME() + 1;

Example

Return the current date and time:

SELECT CURRENT_TIMESTAMP();

Definition and Usage

The CURRENT_TIMESTAMP() function returns the current date and time.

Note: The date and time is returned as "YYYY-MM-DD HH-MM-SS" (string) or as YYYYMMDDHHMMSS.uuuuuu (numeric).

Syntax

CURRENT_TIMESTAMP()

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return the current date and time + 1:

SELECT CURRENT_TIMESTAMP() + 1;

Example

Return current time:

SELECT CURTIME();

Definition and Usage

The CURTIME() function returns the current time.

Note: The time is returned as "HH-MM-SS" (string) or as HHMMSS.uuuuuu (numeric).

Note: This function equals the function.

Syntax

CURTIME()

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return current time + 1:

SELECT CURTIME() + 1;

Example

Extract the date part:

SELECT DATE("2017-06-15");

Definition and Usage

The DATE() function extracts the date part from a datetime expression.

Syntax

DATE(expression)

Parameter Values

Parameter	Description
expression	Required. A valid date/datetime value. Returns NULL if expression is not a date or a datetime

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Extract the date part:

SELECT DATE("2017-06-15 09:34:21");

Example

Extract the date part (will return NULL):

SELECT DATE("The date is 2017-06-15");

Example

Extract the date part:

SELECT DATE(OrderDate) FROM Orders;

Example

Return the number of days between two date values:

SELECT DATEDIFF("2017-06-25", "2017-06-15");

Definition and Usage

The DATEDIFF() function returns the number of days between two date values.

Syntax

DATEDIFF(date1, date2)

Parameter Values

Parameter	Description
date1, date2	Required. Two dates to calculate the number of days between. (date1 - date2)

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return the number of days between two date values:

SELECT DATEDIFF("2017-06-25 09:34:21", "2017-06-15 15:25:35");

Example

Return the number of days between two date values:

SELECT DATEDIFF("2017-01-01", "2016-12-24");

Example

Add 10 days to a date and return the date:

SELECT DATE_ADD("2017-06-15", INTERVAL 10 DAY);

Definition and Usage

The DATE_ADD() function adds a time/date interval to a date and then returns the date.

Syntax

DATE_ADD(date, INTERVAL value addunit)

Parameter Values

Parameter	Description
date	Required. The date to be modified
value	Required. The value of the time/date interval to add. Both positive and negative values are allowed
addunit	Required. The type of interval to add. Can be one of the following values: MICROSECOND SECOND MINUTE HOUR DAY WEEK MONTH QUARTER YEAR SECOND_MICROSECOND MINUTE_MICROSECOND MINUTE_SECOND HOUR_MICROSECOND HOUR_SECOND HOUR_MINUTE DAY_MICROSECOND DAY_SECOND DAY_MINUTE DAY_HOUR YEAR_MONTH

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Add 15 minutes to a date and return the date:

SELECT DATE_ADD("2017-06-15 09:34:21", INTERVAL 15 MINUTE);

Example

Subtract 3 hours to a date and return the date:

SELECT DATE_ADD("2017-06-15 09:34:21", INTERVAL -3 HOUR);

Example

Subtract 2 months to a date and return the date:

SELECT DATE_ADD("2017-06-15", INTERVAL -2 MONTH);

Example

Format a date:

SELECT DATE_FORMAT("2017-06-15", "%Y");

Definition and Usage

The DATE_FORMAT() function formats a date as specified.

Syntax

DATE_FORMAT(date, format)

Parameter Values

Parameter

Description

date

Required. The date to be formatted

format

Required. The format to use. Can be one or a combination of the following values:

Format	Description
%a	Abbreviated weekday name (Sun to Sat)
%b	Abbreviated month name (Jan to Dec)
%c	Numeric month name (0 to 12)
%D	Day of the month as a numeric value, followed by suffix (1st, 2nd, 3rd, ...)
%d	Day of the month as a numeric value (01 to 31)
%e	Day of the month as a numeric value (0 to 31)
%f	Microseconds (000000 to 999999)
%H	Hour (00 to 23)
%h	Hour (00 to 12)
%I	Hour (00 to 12)
%i	Minutes (00 to 59)
%j	Day of the year (001 to 366)
%k	Hour (0 to 23)
%l	Hour (1 to 12)
%M	Month name in full (January to December)
%m	Month name as a numeric value (00 to 12)
%p	AM or PM
%r	Time in 12 hour AM or PM format (hh:mm:ss AM/PM)
%S	Seconds (00 to 59)
%s	Seconds (00 to 59)
%T	Time in 24 hour format (hh:mm:ss)
%U	Week where Sunday is the first day of the week (00 to 53)
%u	Week where Monday is the first day of the week (00 to 53)
%V	Week where Sunday is the first day of the week (01 to 53). Used with %X
%v	Week where Monday is the first day of the week (01 to 53). Used with %x
%W	Weekday name in full (Sunday to Saturday)
%w	Day of the week where Sunday=0 and Saturday=6
%X	Year for the week where Sunday is the first day of the week. Used with %V
%x	Year for the week where Monday is the first day of the week. Used with %v
%Y	Year as a numeric, 4-digit value
%y	Year as a numeric, 2-digit value

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Format a date:

SELECT DATE_FORMAT("2017-06-15", "%M %d %Y");

Example

Format a date:

SELECT DATE_FORMAT("2017-06-15", "%W %M %e %Y");

Example

Format a date:

SELECT DATE_FORMAT(BirthDate, "%W %M %e %Y") FROM Employees;

Example

Subtract 10 days from a date and return the date:

SELECT DATE_SUB("2017-06-15", INTERVAL 10 DAY);

Definition and Usage

The DATE_SUB() function subtracts a time/date interval from a date and then returns the date.

Syntax

DATE_SUB(date, INTERVAL value interval)

Parameter Values

Parameter	Description
date	Required. The date to be modified
value	Required. The value of the time/date interval to subtract. Both positive and negative values are allowed
interval	Required. The type of interval to subtract. Can be one of the following values: MICROSECOND SECOND MINUTE HOUR DAY WEEK MONTH QUARTER YEAR SECOND_MICROSECOND MINUTE_MICROSECOND MINUTE_SECOND HOUR_MICROSECOND HOUR_SECOND HOUR_MINUTE DAY_MICROSECOND DAY_SECOND DAY_MINUTE DAY_HOUR YEAR_MONTH

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Subtract 15 minutes from a date and return the date:

SELECT DATE_SUB("2017-06-15 09:34:21", INTERVAL 15 MINUTE);

Example

Subtract 3 hours from a date and return the date:

SELECT DATE_SUB("2017-06-15 09:34:21", INTERVAL 3 HOUR);

Example

Add 2 months to a date and return the date:

SELECT DATE_SUB("2017-06-15", INTERVAL -2 MONTH);

Example

Return the day of the month for a date:

SELECT DAY("2017-06-15");

Definition and Usage

The DAY() function returns the day of the month for a given date (a number from 1 to 31).

Note: This function equals the function.

Syntax

DAY(date)

Parameter Values

Parameter	Description
date	Required. The date to extract the day from

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return the day of the month for a date:

SELECT DAY("2017-06-15 09:34:21");

Example

Return the day of the month for the current system date:

SELECT DAY(CURDATE());

Example

Return the weekday name for a date:

SELECT DAYNAME("2017-06-15");

Definition and Usage

The DAYNAME() function returns the weekday name for a given date.

Syntax

DAYNAME(date)

Parameter Values

Parameter	Description
date	Required. The date to extract the weekday name from

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return the weekday name for a date:

SELECT DAYNAME("2017-06-15 09:34:21");

Example

Return the weekday name for the current system date:

SELECT DAYNAME(CURDATE());

Example

Return the day of the month for a date:

SELECT DAYOFMONTH("2017-06-15");

Definition and Usage

The DAYOFMONTH() function returns the day of the month for a given date (a number from 1 to 31).

Note: This function equals the function.

Syntax

DAYOFMONTH(date)

Parameter Values

Parameter	Description
date	Required. The date to extract the day from

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return the day of the month for a date:

SELECT DAYOFMONTH("2017-06-15 09:34:21");

Example

Return the day of the month for the current system date:

SELECT DAYOFMONTH(CURDATE());

Example

Return the weekday index for a date:

SELECT DAYOFWEEK("2017-06-15");

Definition and Usage

The DAYOFWEEK() function returns the weekday index for a given date (a number from 1 to 7).

Note: 1=Sunday, 2=Monday, 3=Tuesday, 4=Wednesday, 5=Thursday, 6=Friday, 7=Saturday.

Syntax

DAYOFWEEK(date)

Parameter Values

Parameter	Description
date	Required. The date to return the weekday index from

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return the weekday index for a date:

SELECT DAYOFWEEK("2017-06-15 09:34:21");

Example

Return the weekday index for the current system date:

SELECT DAYOFWEEK(CURDATE());

Example

Return the day of the year for a date:

SELECT DAYOFYEAR("2017-06-15");

Definition and Usage

The DAYOFYEAR() function returns the day of the year for a given date (a number from 1 to 366).

Syntax

DAYOFYEAR(date)

Parameter Values

Parameter	Description
date	Required. The date to return the day of the year from

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return the day of the year for a date:

SELECT DAYOFYEAR("2017-01-01");

Example

Return the day of the year for the current system date:

SELECT DAYOFYEAR(CURDATE());

Example

Extract the month from a date:

SELECT EXTRACT(MONTH FROM "2017-06-15");

Definition and Usage

The EXTRACT() function extracts a part from a given date.

Syntax

EXTRACT(part FROM date)

Parameter Values

Parameter	Description
part	Required. The part to extract. Can be one of the following: MICROSECOND SECOND MINUTE HOUR DAY WEEK MONTH QUARTER YEAR SECOND_MICROSECOND MINUTE_MICROSECOND MINUTE_SECOND HOUR_MICROSECOND HOUR_SECOND HOUR_MINUTE DAY_MICROSECOND DAY_SECOND DAY_MINUTE DAY_HOUR YEAR_MONTH
date	Required. The date to extract a part from

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Extract the week from a date:

SELECT EXTRACT(WEEK FROM "2017-06-15");

Example

Extract the minute from a datetime:

SELECT EXTRACT(MINUTE FROM "2017-06-15 09:34:21");

Example

Extract the year and month from a datetime:

SELECT EXTRACT(YEAR_MONTH FROM "2017-06-15 09:34:21");

Example

Return a date from a numeric representation of the day:

SELECT FROM_DAYS(685467);

Definition and Usage

The FROM_DAYS() function returns a date from a numeric datevalue.

The FROM_DAYS() function is to be used only with dates within the Gregorian calendar.

Note: This function is the opposite of the function.

Syntax

FROM_DAYS(number)

Parameter Values

Parameter	Description
number	Required. The numeric day to convert to a date

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return a date from a numeric representation of the day:

SELECT FROM_DAYS(780500);

Example

Return the hour part of a datetime:

SELECT HOUR("2017-06-20 09:34:00");

Definition and Usage

The HOUR() function returns the hour part for a given date (from 0 to 838).

Syntax

HOUR(datetime)

Parameter Values

Parameter	Description
datetime	Required. The datetime value to extract the hour from

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return the hour part of a datetime:

SELECT HOUR("838:59:59");

Example

Extract the last day of the month for the given date:

SELECT LAST_DAY("2017-06-20");

Definition and Usage

The LAST_DAY() function extracts the last day of the month for a given date.

Syntax

LAST_DAY(date)

Parameter Values

Parameter	Description
date	Required. The date to extract the last day of the month from

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Extract the last day of the month for the given date:

SELECT LAST_DAY("2017-02-10 09:34:00");

Example

Return current date and time:

SELECT LOCALTIME();

Definition and Usage

The LOCALTIME() function returns the current date and time.

Note: The date and time is returned as "YYYY-MM-DD HH-MM-SS" (string) or as YYYYMMDDHHMMSS.uuuuuu (numeric).

Syntax

LOCALTIME()

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return current date and time + 1:

SELECT LOCALTIME() + 1;

Example

Return current date and time:

SELECT LOCALTIMESTAMP();

Definition and Usage

The LOCALTIMESTAMP() function returns the current date and time.

Note: The date and time is returned as "YYYY-MM-DD HH-MM-SS" (string) or as YYYYMMDDHHMMSS.uuuuuu (numeric).

Syntax

LOCALTIMESTAMP()

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return current date and time + 1:

SELECT LOCALTIMESTAMP() + 1;

Example

Create and return a date based on a year and a number of days value:

SELECT MAKEDATE(2017, 3);

Definition and Usage

The MAKEDATE() function creates and returns a date based on a year and a number of days value.

Syntax

MAKEDATE(year, day)

Parameter Values

Parameter	Description
year	Required. A year (4-digits)
day	Required. A number that indicates the day of the year

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Create and return a date based on a year and a number of days value:

SELECT MAKEDATE(2017, 175);

Example

Create and return a date based on a year and a number of days value:

SELECT MAKEDATE(2017, 100);

Example

Create and return a date based on a year and a number of days value:

SELECT MAKEDATE(2017, 366);

Example

Create and return a time value based on an hour, minute, and second value:

SELECT MAKETIME(11, 35, 4);

Definition and Usage

The MAKETIME() function creates and returns a time based on an hour, minute, and second value.

Syntax

MAKETIME(hour, minute, second)

Parameter Values

Parameter	Description
hour	Required. The hour value
minute	Required. The minute value
second	Required. The seconds value

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Create and return a time value based on an hour, minute, and second value:

SELECT MAKETIME(16, 1, 0);

Example

Create and return a time value based on an hour, minute, and second value:

SELECT MAKETIME(21, 59, 59);

Example

Create and return a time value based on an hour, minute, and second value:

SELECT MAKETIME(838, 59, 59);

Example

Return the microsecond part of a datetime:

SELECT MICROSECOND("2017-06-20 09:34:00.000023");

Definition and Usage

The MICROSECOND() function returns the microsecond part of a time/datetime (from 0 to 999999).

Syntax

MICROSECOND(datetime)

Parameter Values

Parameter	Description
datetime	Required. The time or datetime to extract the microsecond from

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return the microsecond part of a time value:

SELECT MICROSECOND("23:59:59.000045");

Example

Return the minute part of a datetime value:

SELECT MINUTE("2017-06-20 09:34:00");

Definition and Usage

The MINUTE() function returns the minute part of a time/datetime (from 0 to 59).

Syntax

MINUTE(datetime)

Parameter Values

Parameter	Description
datetime	Required. The time or datetime extract the minute from

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return the minute part of a time value:

SELECT MINUTE("23:59:59");

Example

Return the month part of a date:

SELECT MONTH("2017-06-15");

Definition and Usage

The MONTH() function returns the month part for a given date (a number from 1 to 12).

Syntax

MONTH(date)

Parameter Values

Parameter	Description
date	Required. The date or datetime to extract the month from

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return the month part of a date:

SELECT MONTH("2017-06-15 09:34:21");

Example

Return the month part of the current system date:

SELECT MONTH(CURDATE());

Example

Return the name of the month for a date:

SELECT MONTHNAME("2017-06-15");

Definition and Usage

The MONTHNAME() function returns the name of the month for a given date.

Syntax

MONTHNAME(date)

Parameter Values

Parameter	Description
date	Required. The date or datetime value to extract the month name from

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return the name of the month for a date:

SELECT MONTHNAME("2017-06-15 09:34:21");

Example

Return the name of the month for the current system date:

SELECT MONTHNAME(CURDATE());

Example

Return current date and time:

SELECT NOW();

Definition and Usage

The NOW() function returns the current date and time.

Note: The date and time is returned as "YYYY-MM-DD HH-MM-SS" (string) or as YYYYMMDDHHMMSS.uuuuuu (numeric).

Syntax

NOW()

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return current date and time + 1:

SELECT NOW() + 1;

Example

Add a specified number of months to a period:

SELECT PERIOD_ADD(201703, 5);

Definition and Usage

The PERIOD_ADD() function adds a specified number of months to a period.

The PERIOD_ADD() function will return the result formatted as YYYYMM.

Syntax

PERIOD_ADD(period, number)

Parameter Values

Parameter	Description
period	Required. A period. Format: YYMM or YYYYMM
number	Required. The number of months to add to period. Both positive and negative values are allowed

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Add a specified number of months to a period:

SELECT PERIOD_ADD(201703, 15);

Example

Add a specified number of months to a period:

SELECT PERIOD_ADD(201703, -2);

Example

Return the difference between two periods:

SELECT PERIOD_DIFF(201710, 201703);

Definition and Usage

The PERIOD_DIFF() function returns the difference between two periods. The result will be in months.

Note: period1 and period2 should be in the same format.

Syntax

PERIOD_DIFF(period1, period2)

Parameter Values

Parameter	Description
period1	Required. A period. Format: YYMM or YYYYMM
period2	Required. Another period. Format: YYMM or YYYYMM

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return the difference between two periods:

SELECT PERIOD_DIFF(201703, 201803);

Example

Return the difference between two periods:

SELECT PERIOD_DIFF(1703, 1612);

Example

Return the quarter of the year for the date:

SELECT QUARTER("2017-06-15");

Definition and Usage

The QUARTER() function returns the quarter of the year for a given date value (a number from 1 to 4).

January-March returns 1
April-June returns 2
July-Sep returns 3
Oct-Dec returns 4

Syntax

QUARTER(date)

Parameter Values

Parameter	Description
date	Required. The date or datetime to extract the quarter from

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return the quarter of the year for the date:

SELECT QUARTER("2017-01-01 09:34:21");

Example

Return the quarter of the year for the date:

SELECT QUARTER(CURDATE());

Example

Return the seconds part of a datetime value:

SELECT SECOND("2017-06-20 09:34:00.000023");

Definition and Usage

The SECOND() function returns the seconds part of a time/datetime (from 0 to 59).

Syntax

SECOND(datetime)

Parameter Values

Parameter	Description
datetime	Required. The time or datetime to extract the second from

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return the seconds part of a time value:

SELECT SECOND("23:59:59");

Example

Return a time value based on a specified seconds value:

SELECT SEC_TO_TIME(1);

Definition and Usage

The SEC_TO_TIME() function returns a time value (in format HH:MM:SS) based on the specified seconds.

Syntax

SEC_TO_TIME(seconds)

Parameter Values

Parameter	Description
seconds	Required. The number of seconds. Both positive or negative values are allowed

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return a time value based on a specified seconds value:

SELECT SEC_TO_TIME(-6897);

Example

Return a date based on a string and a format:

SELECT STR_TO_DATE("August 10 2017", "%M %d %Y");

Definition and Usage

The STR_TO_DATE() function returns a date based on a string and a format.

Syntax

STR_TO_DATE(string, format)

Parameter Values

Parameter

Description

string

Required. The string to be formatted to a date

format

Required. The format to use. Can be one or a combination of the following values:

Format	Description
%a	Abbreviated weekday name (Sun to Sat)
%b	Abbreviated month name (Jan to Dec)
%c	Numeric month name (0 to 12)
%D	Day of the month as a numeric value, followed by suffix (1st, 2nd, 3rd, ...)
%d	Day of the month as a numeric value (01 to 31)
%e	Day of the month as a numeric value (0 to 31)
%f	Microseconds (000000 to 999999)
%H	Hour (00 to 23)
%h	Hour (00 to 12)
%I	Hour (00 to 12)
%i	Minutes (00 to 59)
%j	Day of the year (001 to 366)
%k	Hour (0 to 23)
%l	Hour (1 to 12)
%M	Month name in full (January to December)
%m	Month name as a numeric value (01 to 12)
%p	AM or PM
%r	Time in 12 hour AM or PM format (hh:mm:ss AM/PM)
%S	Seconds (00 to 59)
%s	Seconds (00 to 59)
%T	Time in 24 hour format (hh:mm:ss)
%U	Week where Sunday is the first day of the week (00 to 53)
%u	Week where Monday is the first day of the week (00 to 53)
%V	Week where Sunday is the first day of the week (01 to 53). Used with %X
%v	Week where Monday is the first day of the week (01 to 53). Used with %X
%W	Weekday name in full (Sunday to Saturday)
%w	Day of the week where Sunday=0 and Saturday=6
%X	Year for the week where Sunday is the first day of the week. Used with %V
%x	Year for the week where Monday is the first day of the week. Used with %V
%Y	Year as a numeric, 4-digit value
%y	Year as a numeric, 2-digit value

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return a date based on a string and a format:

SELECT STR_TO_DATE("August,5,2017", "%M %e %Y");

Example

Return a date based on a string and a format:

SELECT STR_TO_DATE("Monday, August 14, 2017", "%W %M %e %Y");

Example

Return a date based on a string and a format:

SELECT STR_TO_DATE("2017,8,14 10,40,10", "%Y,%m,%d %h,%i,%s");

Example

Subtract 10 days from a date and return the date:

SELECT SUBDATE("2017-06-15", INTERVAL 10 DAY);

Definition and Usage

The SUBDATE() function subtracts a time/date interval from a date and then returns the date.

Syntax

SUBDATE(date, INTERVAL value unit)

OR:

SUBDATE(date, days)

Parameter Values

Parameter	Description
date	Required. The original date
days	Required. The number of days to subtract from date
value	Required. The value of the time/date interval to subtract. Both positive and negative values are allowed
unit	Required. The type of interval. Can be one of the following values: MICROSECOND SECOND MINUTE HOUR DAY WEEK MONTH QUARTER YEAR SECOND_MICROSECOND MINUTE_MICROSECOND MINUTE_SECOND HOUR_MICROSECOND HOUR_SECOND HOUR_MINUTE DAY_MICROSECOND DAY_SECOND DAY_MINUTE DAY_HOUR YEAR_MONTH

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Subtract 15 minutes from a date and return the date:

SELECT SUBDATE("2017-06-15 09:34:21", INTERVAL 15 MINUTE);

Example

Subtract 3 hours from a date and return the date:

SELECT SUBDATE("2017-06-15 09:34:21", INTERVAL 3 HOUR);

Example

Add 2 months to a date and return the date:

SELECT SUBDATE("2017-06-15", INTERVAL -2 MONTH);

Example

Subtract 5.000001 seconds and return the datetime:

SELECT SUBTIME("2017-06-15 10:24:21.000004", "5.000001");

Definition and Usage

The SUBTIME() function subtracts time from a time/datetime expression and then returns the new time/datetime.

Syntax

SUBTIME(datetime, time_interval)

Parameter Values

Parameter	Description
datetime	Required. The time or datetime to be modified
time_interval	Required. The time interval to subtract from datetime. Both positive and negative values are allowed

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Subtract 3 hours, 2 minutes, 5.000001 seconds and return the datetime:

SELECT SUBTIME("2017-06-15 10:24:21.000004", "3:2:5.000001");

Example

Subtract 5 seconds and return the time:

SELECT SUBTIME("10:24:21", "5");

Example

Subtract 3 minutes and return the time:

SELECT SUBTIME("10:24:21", "300");

Example

Add 3 hours, 2 minutes, and 5 seconds, and return the time:

SELECT SUBTIME("10:24:21", "-3:2:5");

Example

Return the current date and time:

SELECT SYSDATE();

Definition and Usage

The SYSDATE() function returns the current date and time.

Note: The date and time is returned as "YYYY-MM-DD HH:MM:SS" (string) or as YYYYMMDDHHMMSS (numeric).

Syntax

SYSDATE()

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return the current date and time + 1:

SELECT SYSDATE() + 1;

Example

Extract the time part from a time expression:

SELECT TIME("19:30:10");

Definition and Usage

The TIME() function extracts the time part from a given time/datetime.

Note: This function returns "00:00:00" if expression is not a datetime/time, or NULL if expression is NULL.

Syntax

TIME(expression)

Parameter Values

Parameter	Description
expression	Required. The time/datetime to extract the time from

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Extract the time part from the datetime expression:

SELECT TIME("2017-08-15 19:30:10");

Example

Extract the time part from the datetime expression:

SELECT TIME("2017-08-15 19:30:10.000001");

Example

Extract the time part from NULL:

SELECT TIME(NULL);

Example

Format a time:

SELECT TIME_FORMAT("19:30:10", "%H %i %s");

Definition and Usage

The TIME_FORMAT() function formats a time by a specified format.

Syntax

TIME_FORMAT(time, format)

Parameter Values

Parameter

Description

time

Required. The time to be formatted

format

Required. The format to use. Can be one or a combination of the following:

Format	Description
%f	Microseconds (000000 to 999999)
%H	Hour (00 to 23)
%h	Hour (00 to 12)
%I	Hour (00 to 12)
%i	Minutes (00 to 59)
%p	AM or PM
%r	Time in 12 hour AM or PM format (hh:mm:ss AM/PM)
%S	Seconds (00 to 59)
%s	Seconds (00 to 59)
%T	Time in 24 hour format (hh:mm:ss)

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Format a time:

SELECT TIME_FORMAT("19:30:10", "%h %i %s %p");

Example

Format a time:

SELECT TIME_FORMAT("19:30:10", "%r");

Example

Format a time:

SELECT TIME_FORMAT("19:30:10", "%T");

Example

Convert a time value into seconds:

SELECT TIME_TO_SEC("19:30:10");

Definition and Usage

The TIME_TO_SEC() function converts a time value into seconds.

Syntax

TIME_TO_SEC(time)

Parameter Values

Parameter	Description
time	Required. The time value

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Convert a time value into seconds:

SELECT TIME_TO_SEC("00:00:05");

Example

Convert a time value into seconds:

SELECT TIME_TO_SEC("03:30:00.999999");

Example

Convert a time value into seconds:

SELECT TIME_TO_SEC("-03:30:00");

Example

Return the difference between two time expressions:

SELECT TIMEDIFF("13:10:11", "13:10:10");

Definition and Usage

The TIMEDIFF() function returns the difference between two time/datetime expressions.

Note: time1 and time2 should be in the same format, and the calculation is time1 - time2.

Syntax

TIMEDIFF(time1, time2)

Parameter Values

Parameter	Description
time1	Required. A time value
time2	Required. Another time value

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return the difference between two datetime expressions:

SELECT TIMEDIFF("2017-06-25 13:10:11", "2017-06-15 13:10:10");

Example

Return a datetime value based on the arguments:

SELECT TIMESTAMP("2017-07-23", "13:10:11");

Definition and Usage

The TIMESTAMP() function returns a datetime value based on a date or datetime value.

Note: If there are specified two arguments with this function, it first adds the second argument to the first, and then returns a datetime value.

Syntax

TIMESTAMP(expression, time)

Parameter Values

Parameter	Description
expression	Required. A date or datetime value
time	Optional. A time value to add to expression

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return a datetime value based on the arguments:

SELECT TIMESTAMP("2017-07-23");

Example

Return the number of days between the date and year 0:

SELECT TO_DAYS("2017-06-20");

Definition and Usage

The TO_DAYS() function returns the number of days between a date and year 0 (date "0000-00-00").

The TO_DAYS() function can be used only with dates within the Gregorian calendar.

Note: This function is the opposite of the function.

Syntax

TO_DAYS(date)

Parameter Values

Parameter	Description
date	Required. The given date

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return the number of days between the date and year 0:

SELECT TO_DAYS("2017-06-20 09:34:00");

Example

Return the week number for a date:

SELECT WEEK("2017-06-15");

Definition and Usage

The WEEK() function returns the week number for a given date (a number from 0 to 53).

Syntax

WEEK(date, firstdayofweek)

Parameter Values

Parameter

Description

date

Required. The date or datetime to extract the week number form

firstdayofweek

Optional. Specifies what day the week starts on. Can be one of the following:

0 - First day of week is Sunday
1 - First day of week is Monday and the first week of the year has more than 3 days
2 - First day of week is Sunday
3 - First day of week is Monday and the first week of the year has more than 3 days
4 - First day of week is Sunday and the first week of the year has more than 3 days
5 - First day of week is Monday
6 - First day of week is Sunday and the first week of the year has more than 3 days
7 - First day of week is Monday

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return the week number for a date:

SELECT WEEK("2017-10-25");

Example

Return the week number for the current system date:

SELECT WEEK(CURDATE());

Example

Return the weekday number for a date:

SELECT WEEKDAY("2017-06-15");

Definition and Usage

The WEEKDAY() function returns the weekday number for a given date.

Note: 0 = Monday, 1 = Tuesday, 2 = Wednesday, 3 = Thursday, 4 = Friday, 5 = Saturday, 6 = Sunday.

Syntax

WEEKDAY(date)

Parameter Values

Parameter	Description
date	Required. The date or datetime to extract the weekday number from

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return the weekday number for a date:

SELECT WEEKDAY("2017-01-01");

Example

Return the weekday number for the current system date:

SELECT WEEKDAY(CURDATE());

Example

Return the week number for a date:

SELECT WEEKOFYEAR("2017-06-15");

Definition and Usage

The WEEKOFYEAR() function returns the week number for a given date (a number from 1 to 53).

Note: This function assumes that the first day of the week is Monday and the first week of the year has more than 3 days.

Tip: Also look at the function.

Syntax

WEEKOFYEAR(date)

Parameter Values

Parameter	Description
date	Required. The date or datetime to extract the week number from

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return the week number for a date:

SELECT WEEKOFYEAR("2017-01-01");

Example

Return the week number for the current system date:

SELECT WEEKOFYEAR(CURDATE());

Example

Return the year part of a date:

SELECT YEAR("2017-06-15");

Definition and Usage

The YEAR() function returns the year part for a given date (a number from 1000 to 9999).

Syntax

YEAR(date)

Parameter Values

Parameter	Description
date	Required. The date/datetime to extract the year from

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return the year part of a date:

SELECT YEAR("2017-06-15 09:34:21");

Example

Return the year part of the current system date:

SELECT YEAR(CURDATE());

Example

Return the year and week number for a date:

SELECT YEARWEEK("2017-06-15");

Definition and Usage

The YEARWEEK() function returns the year and week number (a number from 0 to 53) for a given date.

Syntax

YEARWEEK(date, firstdayofweek)

Parameter Values

Parameter

Description

date

Required. The date or datetime value to extract the year and week number from

firstdayofweek

Optional. Specifies what day the week starts on. Can be one of the following:

0 - First day of week is Sunday
1 - First day of week is Monday and the first week has more than 3 days
2 - First day of week is Sunday
3 - First day of week is Monday and the first week has more than 3 days
4 - First day of week is Sunday and the first week has more than 3 days
5 - First day of week is Monday
6 - First day of week is Sunday and the first week has more than 3 days
7 - First day of week is Monday

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return the year and week number for a date:

SELECT YEARWEEK("2017-10-25");

Example

Return the year and week number for the current system date:

SELECT YEARWEEK(CURDATE());

Example

Return a binary representation of 15:

SELECT BIN(15);

Definition and Usage

The BIN() function returns a binary representation of a number, as a string value.

Syntax

BIN(number)

Parameter Values

Parameter	Description
number	Required. A number

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return a binary representation of 111:

SELECT BIN(111);

Example

Return a binary representation of 8:

SELECT BIN(8);

Example

Convert a value to a binary string:

SELECT BINARY "W3Schools.com";

Definition and Usage

The BINARY function converts a value to a binary string.

This function is equivalent to using .

Syntax

BINARY value

Parameter Values

Parameter	Description
value	Required. The value to convert

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Here MySQL performs a character-by-character comparison of "HELLO" and "hello" and return 1 (because on a character-by-character basis, they are equivalent):

SELECT "HELLO" = "hello";

Example

Here MySQL performs a byte-by-byte comparison of "HELLO" and "hello" and return 0 (because on a byte-by-byte basis, they are NOT equivalent):

SELECT BINARY "HELLO" = "hello";

Example

Go through conditions and return a value when the first condition is met:

SELECT OrderID, Quantity,
CASE
    WHEN Quantity > 30 THEN "The quantity is greater than 30"
    WHEN Quantity = 30 THEN "The quantity is 30"
    ELSE "The quantity is under 30"
END
FROM OrderDetails;

Definition and Usage

The CASE statement goes through conditions and return a value when the first condition is met (like an IF-THEN-ELSE statement). So, once a condition is true, it will stop reading and return the result.

If no conditions are true, it will return the value in the ELSE clause.

If there is no ELSE part and no conditions are true, it returns NULL.

Syntax

CASE
    WHEN condition1 THEN result1
    WHEN condition2 THEN result2
    WHEN conditionN THEN resultN
    ELSE result
END;

Parameter Values

Parameter	Description
condition1, condition2, ...conditionN	Required. The conditions. These are evaluated in the same order as they are listed
result1, result2, ...resultN	Required. The value to return once a condition is true

Technical Details

Works in:	From MySQL 4.0

More Examples

The following SQL will order the customers by City. However, if City is NULL, then order by Country:

Example

SELECT CustomerName, City, Country
FROM Customers
ORDER BY
(CASE
WHEN City IS NULL THEN Country
ELSE City
END);

Example

Convert a value to a DATE datatype:

SELECT CAST("2017-08-29" AS DATE);

Definition and Usage

The CAST() function converts a value (of any type) into the specified datatype.

Tip: See also the function.

Syntax

CAST(value AS datatype)

Parameter Values

Parameter

Description

value

Required. The value to convert

datatype

Required. The datatype to convert to. Can be one of the following:

Value	Description
DATE	Converts value to DATE. Format: "YYYY-MM-DD"
DATETIME	Converts value to DATETIME. Format: "YYYY-MM-DD HH:MM:SS"
DECIMAL	Converts value to DECIMAL. Use the optional M and D parameters to specify the maximum number of digits (M) and the number of digits following the decimal point (D).
TIME	Converts value to TIME. Format: "HH:MM:SS"
CHAR	Converts value to CHAR (a fixed length string)
NCHAR	Converts value to NCHAR (like CHAR, but produces a string with the national character set)
SIGNED	Converts value to SIGNED (a signed 64-bit integer)
UNSIGNED	Converts value to UNSIGNED (an unsigned 64-bit integer)
BINARY	Converts value to BINARY (a binary string)

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Convert a value to a CHAR datatype:

SELECT CAST(150 AS CHAR);

Example

Convert a value to a TIME datatype:

SELECT CAST("14:06:10" AS TIME);

Example

Convert a value to a SIGNED datatype:

SELECT CAST(5-10 AS SIGNED);

Example

Return the first non-null value in a list:

SELECT COALESCE(NULL, NULL, NULL, 'W3Schools.com', NULL, 'Example.com');

Definition and Usage

The COALESCE() function returns the first non-null value in a list.

Syntax

COALESCE(val1, val2, ...., val_n)

Parameter Values

Parameter	Description
val1, val2, val_n	Required. The values to test

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return the first non-null value in a list:

SELECT COALESCE(NULL, 1, 2, 'W3Schools.com');

Example

Return the unique connection ID for the current connection:

SELECT CONNECTION_ID();

Definition and Usage

The CONNECTION_ID() function returns the unique connection ID for the current connection.

Syntax

CONNECTION_ID()

Technical Details

Works in:	From MySQL 4.0

Example

Convert a number from numeric base system 10 to numeric base system 2:

SELECT CONV(15, 10, 2);

Definition and Usage

The CONV() function converts a number from one numeric base system to another, and returns the result as a string value.

Note: This function returns NULL if any of the parameters are NULL.

Tip: Also look at the function.

Syntax

CONV(number, from_base, to_base)

Parameter Values

Parameter	Description
number	Required. A number
from_base	The numeric base system of number (a number between 2 and 36)
to_base	The numeric base system to convert to (a number between 2 and 36 or -2 and -36)

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Convert a number from numeric base system 2 to numeric base system 10:

SELECT CONV(1111, 2, 10);

Example

Convert a number from numeric base system 10 to numeric base system 16:

SELECT CONV(88, 10, 16);

Example

Convert a value to a DATE datatype:

SELECT CONVERT("2017-08-29", DATE);

Definition and Usage

The CONVERT() function converts a value into the specified datatype or character set.

Tip: Also look at the function.

Syntax

CONVERT(value, type)

OR:

CONVERT(value USING charset)

Parameter Values

Parameter

Description

value

Required. The value to convert

type

Required. The datatype to convert to. Can be one of the following:

Value	Description
DATE	Converts value to DATE. Format: "YYYY-MM-DD"
DATETIME	Converts value to DATETIME. Format: "YYYY-MM-DD HH:MM:SS"
DECIMAL	Converts value to DECIMAL. Use the optional M and D parameters to specify the maximum number of digits (M) and the number of digits following the decimal point (D).
TIME	Converts value to TIME. Format: "HH:MM:SS"
CHAR	Converts value to CHAR (a fixed length string)
NCHAR	Converts value to NCHAR (like CHAR, but produces a string with the national character set)
SIGNED	Converts value to SIGNED (a signed 64-bit integer)
UNSIGNED	Converts value to UNSIGNED (an unsigned 64-bit integer)
BINARY	Converts value to BINARY (a binary string)

charset

Required. The character set to convert to

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Convert a value to a CHAR datatype:

SELECT CONVERT(150, CHAR);

Example

Convert a value to a TIME datatype:

SELECT CONVERT("14:06:10", TIME);

Example

Convert a value to LATIN1 character set:

SELECT CONVERT("W3Schools.com" USING latin1);

Example

Return the user name and host name for the MySQL account:

SELECT CURRENT_USER();

Definition and Usage

The CURRENT_USER() function returns the user name and host name for the MySQL account that the server used to authenticate the current client.

The result is returned as a string in the UTF8 character set.

Tip: See also the function.

Syntax

CURRENT_USER()

Technical Details

Works in:	From MySQL 4.0

Example

Return the name of the current (default) database:

SELECT DATABASE();

Definition and Usage

The DATABASE() function returns the name of the current database.

If there is no current database, this function returns NULL or "".

Syntax

DATABASE()

Technical Details

Works in:	From MySQL 4.0

Example

Return "YES" if the condition is TRUE, or "NO" if the condition is FALSE:

SELECT IF(500<1000, "YES", "NO");

Definition and Usage

The IF() function returns a value if a condition is TRUE, or another value if a condition is FALSE.

Syntax

IF(condition, value_if_true, value_if_false)

Parameter Values

Parameter	Description
condition	Required. The value to test
value_if_true	Required. The value to return if condition is TRUE
value_if_false	Required. The value to return if condition is FALSE

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return 5 if the condition is TRUE, or 10 if the condition is FALSE:

SELECT IF(500<1000, 5, 10);

Example

Test whether two strings are the same and return "YES" if they are, or "NO" if not:

SELECT IF(STRCMP("hello","bye") = 0, "YES", "NO");

Example

Return "MORE" if the condition is TRUE, or "LESS" if the condition is FALSE:

SELECT OrderID, Quantity, IF(Quantity>10, "MORE", "LESS")
FROM OrderDetails;

Example

Return the specified value IF the expression is NULL, otherwise return the expression:

SELECT IFNULL(NULL, "W3Schools.com");

Definition and Usage

The IFNULL() function returns a specified value if the expression is NULL.

If the expression is NOT NULL, this function returns the expression.

Syntax

IFNULL(expression, alt_value)

Parameter Values

Parameter	Description
expression	Required. The expression to test whether is NULL
alt_value	Required. The value to return if expression is NULL

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Return the specified value IF the expression is NULL, otherwise return the expression:

SELECT IFNULL("Hello", "W3Schools.com");

Example

Return the specified value IF the expression is NULL, otherwise return the expression:

SELECT IFNULL(NULL, 500);

Example

Test whether an expression is NULL:

SELECT ISNULL(NULL);

Definition and Usage

The ISNULL() function returns 1 or 0 depending on whether an expression is NULL.

If expression is NULL, this function returns 1. Otherwise, it returns 0.

Syntax

ISNULL(expression)

Parameter Values

Parameter	Description
expression	Required. The value to test

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Test whether an expression is NULL:

SELECT ISNULL("");

Example

Test whether an expression is NULL:

SELECT ISNULL(350);

Example

Test whether an expression is NULL:

SELECT ISNULL("Hello world!");

Example

Return the AUTO_INCREMENT id of the last row that has been inserted or updated in a table:

SELECT LAST_INSERT_ID();

Definition and Usage

The LAST_INSERT_ID() function returns the AUTO_INCREMENT id of the last row that has been inserted or updated in a table.

Syntax

LAST_INSERT_ID(expression)

Parameter Values

Parameter	Description
expression	Optional. An expression

Technical Details

Works in:	From MySQL 4.0

Example

Compare two expressions:

SELECT NULLIF(25, 25);

Definition and Usage

The NULLIF() function compares two expressions and returns NULL if they are equal. Otherwise, the first expression is returned.

Syntax

NULLIF(expr1, expr2)

Parameter Values

Parameter	Description
expr1, expr2	Required. The two expressions to be compared

Technical Details

Works in:	From MySQL 4.0

More Examples

Example

Compare two expressions:

SELECT NULLIF(25, "Hello");

Example

Compare two expressions:

SELECT NULLIF("Hello", "world");

Example

Compare two expressions:

SELECT NULLIF("2017-08-25", "2017-08-25");

Example

Return the current user name and host name for the MySQL connection:

SELECT SESSION_USER();

Definition and Usage

The SESSION_USER() function returns the current user name and host name for the MySQL connection.

Note: This function is equal to the and the function.

Syntax

SESSION_USER()

Technical Details

Works in:	From MySQL 4.0

Example

Return the current user name and host name for the MySQL connection:

SELECT SYSTEM_USER();

Definition and Usage

The SYSTEM_USER() function returns the current user name and host name for the MySQL connection.

Note: This function is equal to the function and the function.

Syntax

SYSTEM_USER()

Technical Details

Works in:	From MySQL 4.0

Example

Return the current user name and host name for the MySQL connection:

SELECT USER();

Definition and Usage

The USER() function returns the current user name and host name for the MySQL connection.

Note: This function is equal to the function and the function.

Tip: Also look at the function.

Syntax

USER()

Technical Details

Works in:	From MySQL 4.0

Example

Return the current version of the MySQL database:

SELECT VERSION();

Definition and Usage

The VERSION() function returns the current version of the MySQL database, as a string.

Syntax

VERSION()

Technical Details

Works in:	From MySQL 4.0

SQL Server Functions

SQL Server has many built-in functions.

This reference contains string, numeric, date, conversion, and some advanced functions in SQL Server.

SQL Server String Functions

Function	Description
	Returns the ASCII value for the specific character
	Returns the character based on the ASCII code
	Returns the position of a substring in a string
	Adds two or more strings together
	Adds two or more strings together
	Adds two or more strings together with a separator
	Returns the number of bytes used to represent an expression
	Compares two SOUNDEX values, and returns an integer value
	Formats a value with the specified format
	Extracts a number of characters from a string (starting from left)
	Returns the length of a string
	Converts a string to lower-case
	Removes leading spaces from a string
	Returns the Unicode character based on the number code
	Returns the position of a pattern in a string
	Returns a Unicode string with delimiters added to make the string a valid SQL Server delimited identifier
	Replaces all occurrences of a substring within a string, with a new substring
	Repeats a string a specified number of times
	Reverses a string and returns the result
	Extracts a number of characters from a string (starting from right)
	Removes trailing spaces from a string
	Returns a four-character code to evaluate the similarity of two strings
	Returns a string of the specified number of space characters
	Returns a number as string
	Deletes a part of a string and then inserts another part into the string, starting at a specified position
	Extracts some characters from a string
	Returns the string from the first argument after the characters specified in the second argument are translated into the characters specified in the third argument.
	Removes leading and trailing spaces (or other specified characters) from a string
	Returns the Unicode value for the first character of the input expression
	Converts a string to upper-case

SQL Server Math/Numeric Functions

Function	Description
	Returns the absolute value of a number
	Returns the arc cosine of a number
	Returns the arc sine of a number
	Returns the arc tangent of a number
	Returns the arc tangent of two numbers
	Returns the average value of an expression
	Returns the smallest integer value that is >= a number
	Returns the number of records returned by a select query
	Returns the cosine of a number
	Returns the cotangent of a number
	Converts a value in radians to degrees
	Returns e raised to the power of a specified number
	Returns the largest integer value that is <= to a number
	Returns the natural logarithm of a number, or the logarithm of a number to a specified base
	Returns the natural logarithm of a number to base 10
	Returns the maximum value in a set of values
	Returns the minimum value in a set of values
	Returns the value of PI
	Returns the value of a number raised to the power of another number
	Converts a degree value into radians
	Returns a random number
	Rounds a number to a specified number of decimal places
	Returns the sign of a number
	Returns the sine of a number
	Returns the square root of a number
	Returns the square of a number
	Calculates the sum of a set of values
	Returns the tangent of a number

SQL Server Date Functions

Function	Description
	Returns the current date and time
	Adds a time/date interval to a date and then returns the date
	Returns the difference between two dates
	Returns a date from the specified parts (year, month, and day values)
	Returns a specified part of a date (as string)
	Returns a specified part of a date (as integer)
	Returns the day of the month for a specified date
	Returns the current database system date and time
	Returns the current database system UTC date and time
	Checks an expression and returns 1 if it is a valid date, otherwise 0
	Returns the month part for a specified date (a number from 1 to 12)
	Returns the date and time of the SQL Server
	Returns the year part for a specified date

SQL Server Advanced Functions

Function	Description
	Converts a value (of any type) into a specified datatype
	Returns the first non-null value in a list
	Converts a value (of any type) into a specified datatype
	Returns the name of the current user in the SQL Server database
	Returns a value if a condition is TRUE, or another value if a condition is FALSE
	Return a specified value if the expression is NULL, otherwise return the expression
	Tests whether an expression is numeric
	Returns NULL if two expressions are equal
	Returns the name of the current user in the SQL Server database
	Returns the session settings for a specified option
	Returns the login name for the current user
	Returns the database user name based on the specified id

MS Access Functions

MS Access has many built-in functions.

This reference contains the string, numeric, and date functions in MS Access.

MS Access String Functions

Function	Description
	Returns the ASCII value for the specific character
	Returns the character for the specified ASCII number code
	Adds two or more strings together
	Returns the full path for a specified drive
	Formats a value with the specified format
	Gets the position of the first occurrence of a string in another
	Gets the position of the first occurrence of a string in another, from the end of string
	Converts a string to lower-case
	Extracts a number of characters from a string (starting from left)
	Returns the length of a string
	Removes leading spaces from a string
	Extracts some characters from a string (starting at any position)
	Replaces a substring within a string, with another substring, a specified number of times
	Extracts a number of characters from a string (starting from right)
	Removes trailing spaces from a string
	Returns a string of the specified number of space characters
	Splits a string into an array of substrings
	Returns a number as string
	Compares two strings
	Returns a converted string
	Reverses a string and returns the result
	Removes both leading and trailing spaces from a string
	Converts a string to upper-case

MS Access Numeric Functions

Function	Description
	Returns the absolute value of a number
	Returns the arc tangent of a number
	Returns the average value of an expression
	Returns the cosine of an angle
	Returns the number of records returned by a select query
	Returns e raised to the power of a specified number
	Returns the integer part of a number
	Formats a numeric value with the specified format
	Returns the integer part of a number
	Returns the maximum value in a set of values
	Returns the minimum value in a set of values
	Initializes the random number generator (used by Rnd()) with a seed
	Returns a random number
	Rounds a number to a specified number of decimal places
	Returns the sign of a number
	Returns the square root of a number
	Calculates the sum of a set of values
	Reads a string and returns the numbers found in the string

MS Access Date Functions

Function	Description
	Returns the current system date
	Adds a time/date interval to a date and then returns the date
	Returns the difference between two dates
	Returns a specified part of a date (as an integer)
	Returns a date from the specified parts (year, month, and day values)
	Returns a date based on a string
	Returns the day of the month for a given date
	Formats a date value with the specified format
	Returns the hour part of a time/datetime
	Returns the minute part of a time/datetime
	Returns the month part of a given date
	Returns the name of the month based on a number
	Returns the current date and time based on the computer's system date and time
	Returns the seconds part of a time/datetime
	Returns the current system time
	Returns a time from the specified parts (hour, minute, and second value)
	Returns a time based on a string
	Returns the weekday number for a given date
	Returns the weekday name based on a number
	Returns the year part of a given date

MS Access Some Other Functions

Function	Description
	Returns the name of the current database user
	Returns a string that contains the value of an operating system environment variable
	Checks whether an expression can be converted to a date
	Checks whether an expression contains Null (no data)
	Checks whether an expression is a valid number

SQL Statement	Syntax
AND / OR	SELECT column_name(s) FROM table_name WHERE condition AND\|OR condition
ALTER TABLE	ALTER TABLE table_name ADD column_name datatype or ALTER TABLE table_name DROP COLUMN column_name
AS (alias)	SELECT column_name AS column_alias FROM table_name or SELECT column_name FROM table_name AS table_alias
BETWEEN	SELECT column_name(s) FROM table_name WHERE column_name BETWEEN value1 AND value2
CREATE DATABASE	CREATE DATABASE database_name
CREATE TABLE	CREATE TABLE table_name ( column_name1 data_type, column_name2 data_type, column_name3 data_type, ... )
CREATE INDEX	CREATE INDEX index_name ON table_name (column_name) or CREATE UNIQUE INDEX index_name ON table_name (column_name)
CREATE VIEW	CREATE VIEW view_name AS SELECT column_name(s) FROM table_name WHERE condition
DELETE	DELETE FROM table_name WHERE some_column=some_value or DELETE FROM table_name (Note: Deletes the entire table!!) DELETE * FROM table_name (Note: Deletes the entire table!!)
DROP DATABASE	DROP DATABASE database_name
DROP INDEX	DROP INDEX table_name.index_name (SQL Server) DROP INDEX index_name ON table_name (MS Access) DROP INDEX index_name (DB2/Oracle) ALTER TABLE table_name DROP INDEX index_name (MySQL)
DROP TABLE	DROP TABLE table_name
EXISTS	IF EXISTS (SELECT * FROM table_name WHERE id = ?) BEGIN --do what needs to be done if exists END ELSE BEGIN --do what needs to be done if not END
GROUP BY	SELECT column_name, aggregate_function(column_name) FROM table_name WHERE column_name operator value GROUP BY column_name
HAVING	SELECT column_name, aggregate_function(column_name) FROM table_name WHERE column_name operator value GROUP BY column_name HAVING aggregate_function(column_name) operator value
IN	SELECT column_name(s) FROM table_name WHERE column_name IN (value1,value2,..)
INSERT INTO	INSERT INTO table_name VALUES (value1, value2, value3,....) or INSERT INTO table_name (column1, column2, column3,...) VALUES (value1, value2, value3,....)
INNER JOIN	SELECT column_name(s) FROM table_name1 INNER JOIN table_name2 ON table_name1.column_name=table_name2.column_name
LEFT JOIN	SELECT column_name(s) FROM table_name1 LEFT JOIN table_name2 ON table_name1.column_name=table_name2.column_name
RIGHT JOIN	SELECT column_name(s) FROM table_name1 RIGHT JOIN table_name2 ON table_name1.column_name=table_name2.column_name
FULL JOIN	SELECT column_name(s) FROM table_name1 FULL JOIN table_name2 ON table_name1.column_name=table_name2.column_name
LIKE	SELECT column_name(s) FROM table_name WHERE column_name LIKE pattern
ORDER BY	SELECT column_name(s) FROM table_name ORDER BY column_name [ASC\|DESC]
SELECT	SELECT column_name(s) FROM table_name
SELECT *	SELECT * FROM table_name
SELECT DISTINCT	SELECT DISTINCT column_name(s) FROM table_name
SELECT INTO	SELECT * INTO new_table_name [IN externaldatabase] FROM old_table_name or SELECT column_name(s) INTO new_table_name [IN externaldatabase] FROM old_table_name
SELECT TOP	SELECT TOP number\|percent column_name(s) FROM table_name
TRUNCATE TABLE	TRUNCATE TABLE table_name
UNION	SELECT column_name(s) FROM table_name1 UNION SELECT column_name(s) FROM table_name2
UNION ALL	SELECT column_name(s) FROM table_name1 UNION ALL SELECT column_name(s) FROM table_name2
UPDATE	UPDATE table_name SET column1=value, column2=value,... WHERE some_column=some_value
WHERE	SELECT column_name(s) FROM table_name WHERE column_name operator value

Source : https://www.w3schools.com/sql/sql_quickref.asp

SQL Examples

SQL Syntax

SQL SELECT

SQL SELECT DISTINCT

SQL WHERE

SQL AND, OR and NOT Operators

SQL ORDER BY

SQL INSERT INTO

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SQL LIKE

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SQL BETWEEN

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SQL Joins

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SQL Comments

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2	Centro comercial Moctezuma	Francisco Chang	Mexico
3	Ernst Handel	Roland Mendel	Austria

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How it Works

1. Application and Enrollment:
Reserve your seat and enroll in the bootcamp by paying the bootcamp fee of only $495. The price includes the exam fee and 18 hours with live instructor.

2. Complete the Bootcamp:
After enrollment, you will be placed in a learning cohort with other students. You will go through the course material together and complete assignments and projects with the help of an experienced instructor.

The bootcamp covers the fundamentals of SQL. The curriculum used is the . The bootcamp will help you prepare for the W3Schools SQL exam so that you can document and validate your competence.

Throughout the bootcamp, you will receive support from your cohort and the W3Schools team to help you grow your skill set.

3. Certification and Job Application:
Upon completing the bootcamp, you will have passed the W3Schools SQL exam and obtained the Certified SQL Developer Title and an extra acknowledgement that you were a part of the bootcamp on the certification. This certification demonstrates that you know the fundamentals of SQL.

W3Schools SQL Certificate

W3Schools offers an Online Certification Program.

The perfect solution for busy professionals who need to balance work, family, and career building.

More than 50 000 certificates already issued!

W3Schools offers an Online Certification Program.

The perfect solution for busy professionals who need to balance work, family, and career building.

More than 50 000 certificates already issued!

Document your skills
Improve your career

Study at your own pace
Save time and money

Known brand
Trusted by top companies

Who Should Consider Getting Certified?

Any student or professional within the digital industry.

Certifications are valuable assets to gain trust and demonstrate knowledge to your clients, current or future employers on a ever increasing competitive market.

W3Schools is Trusted by Top Companies

W3Schools has over two decades of experience with teaching coding online.

Our certificates are recognized and valued by companies looking to employ skilled developers.

Save Time and Money

Show the world your coding skills by getting a certification.

The prices is a small fraction compared to the price of traditional education.

Document and validate your competence by getting certified!

Exam overview

Fee: 95 USD

Number of questions: 70

Requirement to pass: 75% correct answers

Time limit: 70 minutes

Number of attempts to pass: Two

Exam deadline: None

Certification Expiration: None

Format: Online, multiple choice

Advance Faster in Your Career

Getting a certificate proves your commitment to upgrading your skills.

The certificate can be added as credentials to your CV, Resume, LinkedIn profile, and so on.

It gives you the credibility needed for more responsibilities, larger projects, and a higher salary.

Knowledge is power, especially in the current job market.

Documentation of your skills enables you to advance your career or helps you to start a new one.

How Does It Work?

Study for free at W3Schools.com
Study at your own speed
Test your skills with W3Schools online quizzes
Apply for your certificate by paying an exam fee
Take your exam online, at any time, and from any location

Get Your Certificate and Share It With The World

Example certificate:

Each certificate gets a unique link that can be shared with others.

Validate your certification with the link or QR code.

Check how it looks like in this .

Share your certificate on LinkedIn in the Certifications section in just one click!

Document Your Skills

Getting a certificate proves your commitment to upgrade your skills, gives you the credibility needed for more responsibilities, larger projects, and a higher salary.

Looking to add multiple users?

Are you an educator, manager or business owner looking for courses or certifications?

We are working with schools, companies and organizations from all over the world.

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