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Select With a Filter

When selecting records from a table, you can filter the selection by using the "WHERE" statement:

Example

Select record(s) with the address "Park Lane 38":

var mysql = require('mysql');

var con = mysql.createConnection({
  host: "localhost",
  user: "yourusername",
  password: "yourpassword",
  database: "mydb"
});

con.connect(function(err) {
  if (err) throw err;
  con.query("SELECT * FROM customers WHERE address = 'Park Lane 38'", function (err, result) {
    if (err) throw err;
    console.log(result);
  });
});

Save the code above in a file called "demo_db_where.js" and run the file:

Run "demo_db_where.js"

C:UsersYour Name>node demo_db_where.js

Which will give you this result:

[
  { id: 11, name: 'Ben', address: 'Park Lane 38'}
]

Wildcard Characters

You can also select the records that starts, includes, or ends with a given letter or phrase.

Use the '%' wildcard to represent zero, one or multiple characters:

Example

Select records where the address starts with the letter 'S':

var mysql = require('mysql');

var con = mysql.createConnection({
  host: "localhost",
  user: "yourusername",
  password: "yourpassword",
  database: "mydb"
});

con.connect(function(err) {
  if (err) throw err;
  con.query("SELECT * FROM customers WHERE address LIKE 'S%'", function (err, result) {
    if (err) throw err;
    console.log(result);
  });
});

Save the code above in a file called "demo_db_where_s.js" and run the file:

Run "demo_db_where_s.js"

C:UsersYour Name>node demo_db_where_s.js

Which will give you this result:

[
  { id: 8, name: 'Richard', address: 'Sky st 331'},
  { id: 14, name: 'Viola', address: 'Sideway 1633'}
]

Escaping Query Values

When query values are variables provided by the user, you should escape the values.

This is to prevent SQL injections, which is a common web hacking technique to destroy or misuse your database.

The MySQL module has methods to escape query values:

Example

Escape query values by using the mysql.escape() method:

var adr = 'Mountain 21';
var sql = 'SELECT * FROM customers WHERE address = ' + mysql.escape(adr);
con.query(sql, function (err, result) {
  if (err) throw err;
  console.log(result);
});

You can also use a ? as a placeholder for the values you want to escape.

In this case, the variable is sent as the second parameter in the query() method:

Example

Escape query values by using the placeholder ? method:

var adr = 'Mountain 21';
var sql = 'SELECT * FROM customers WHERE address = ?';
con.query(sql, [adr], function (err, result) {
  if (err) throw err;
  console.log(result);
});

If you have multiple placeholders, the array contains multiple values, in that order:

Example

Multiple placeholders:

var name = 'Amy';
var adr = 'Mountain 21';
var sql = 'SELECT * FROM customers WHERE name = ? OR address = ?';
con.query(sql, [name, adr], function (err, result) {
  if (err) throw err;
  console.log(result);
});
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