SQL ALTER TABLE Statement

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);
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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;
Try it Yourself »

ALTER TABLE - ALTER/MODIFY COLUMN

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;