ALTER TABLE

The ALTER TABLE statement is used to add or drop columns in an existing table.

ALTER TABLE table_name
ADD column_name datatype

ALTER TABLE table_name
DROP COLUMN column_name

Note: Some database systems don't allow the dropping of a column in a database table (DROP COLUMN column_name).

Person:
LastName FirstName Address
Pettersen Kari Storgt 20

Example

To add a column named "City" in the "Person" table:

ALTER TABLE Person ADD City varchar(30)

Result:
LastName FirstName Address City
Pettersen Kari Storgt 20
Example

To drop the "Address" column in the "Person" table:

ALTER TABLE Person DROP COLUMN Address

Result:
LastName FirstName City
Pettersen Kari