Sams Teach Yourself SQL in 10 Minutes

ALTER TABLE

ALTER TABLE is used to update the schema of an existing table. To create a new table, use CREATE TABLE. See Lesson 17, "Creating and Manipulating Tables," for more information.

ALTER TABLE tablename
(
   ADD|DROP   column   datatype   [NULL|NOT NULL] [CONSTRAINTS],
   ADD|DROP   column   datatype   [NULL|NOT NULL] [CONSTRAINTS],
   …
);