Usage and Examples of SQL ALTER TABLE Keywords

SQL Keyword Reference

ALTER TABLE

The ALTER TABLE command adds, deletes, or modifies columns in the table.

The ALTER TABLE command also adds and deletes various constraints in the table.

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

　　ALTER TABLE Customers
ADD Email varchar(255);

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

　　ALTER TABLE Customers
DROP COLUMN Email;

SQL Keyword Reference