SQL Check Constraint
A SQL Check constraint enforce domain integrity by limiting the values that are accepted by one or more columns.
Multiple CHECK constraints can be created for a single column. Also you can create a single CHECK constraint to multiple columns by creating it at the table level.
CHECK constraints reject values that evaluate to FALSE.
A CHECK constraint returns TRUE when the condition it is checking is not FALSE for any row in the table.
CREATE TABLE Training_Course ( ID INT PRIMARY KEY, NAME VARCHAR(250) NOT NULL, DURATION INT, PRICE INT ); ALTER TABLE Training_Course ADD CONSTRAINT CHK_TC CHECK (DURATION > 4 and PRICE < 500 ); INSERT INTO Training_Course(ID, NAME, DURATION, PRICE) values(1,'SQL',5,200); (1 row(s) affected) INSERT INTO Training_Course(ID, NAME, DURATION, PRICE) values(2,'T-SQL',7,700); The INSERT statement conflicted with the CHECK constraint "CHK_TC". The conflict occurred in database "model", table "dbo.Training_Course".
Drop Check Constraint
ALTER TABLE Training_Course DROP CONSTRAINT CHK_TC;