Sometimes we need to add ulterior constraints to the table we define. The ALTER TABLE statement enables us to do this. There are several types of constraints we can add. If we want to ensure that all ...

--Column u silme ALTER TABLE Teachers1 DROP COLUMN IdPost ADD CONSTRAINT HireDate_Before_1990 CHECK (HireDate <= '1990-01-01 ') ALTER TABLE Teachers1 ADD CONSTRAINT UNK_CODE UNIQUE (Code) ALTER TABLE ...