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The ALTER TABLE Statement

To add a column to an existing table, we have to use the 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.

ADD COLUMN

We want to add a column named color to our cars table.

When adding columns we must also specify the data type of the column. Our color column will be a string, and we specify string types with the VARCHAR keyword. we also want to restrict the number of characters to 255:

Example

Add a column named color:

ALTER TABLE cars
ADD color VARCHAR(255);

Result

ALTER TABLE

Display Table

To check the result we can display the table with this SQL statement:

Example

SELECT * FROM cars;

As you can see, the cars table now has a color column.

The new column is empty, you will learn how to fill it with values in the .

PostgreSQL Exercises

Test Yourself With Exercises

Exercise:

Write the correct SQL statement to add a column named colors to the cars table:

 cars
 color VARCHAR(255);

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