-- HERE IS THE SIMPLE DEMONSTRATION CHECK CONSTRAINT WITH USER DEFINED FUNCTION. -- SENARIO : ONLY ONE STUDENT CAN JOIN THE AT A TIME . ALL STUDENTS CAN WAIT UNTILL THE JOINED STUDENT CAN INACTIVE. -- CREATE FUNCTION CREATE FUNCTION CHECK_StudentJoinSQLClass ( @JOINED BIT ) RETURNS BIT AS BEGIN IF ( @JOINED = 1 AND ( SELECT COUNT (*) FROM StudentJoinSQLClass WHERE JOINED = @JOINED )> 1 ) BEGIN SET @JOINED = 0 --FALSE END ELSE BEGIN SET @JOINED = 1 --TRUE END RETURN @JOINED END -- CREATE TABLE CREATE TABLE StudentJoinSQLClass ( ID INT IDENTITY ( 1 , 1 ), NAME VARCHAR ( 10 ), JOINED BIT NOT NULL CHECK ( DBO . CHECK_StudentJoinSQLClass ( JOINED )= 1 ) ) --INSERT DATA INSE...