T-SQL触发器

/*

 * 触发器: 是一种特殊的存储过程

 *   必须依附于表或者视图

 *   不能被显式调用

 *   当对表或视图执行insert,update,delete操作自动引发

 *

 * 优点:

 *  1.自动执行

 *  2.强化约束

 *  3.级联操作

 *

 * 类型:

 *  AFTER

 *  INSTEAD OF

 *

 * 引发触发器的操作

 *  INSERT

 *  UPDATE

 *  DELETE

 */

 

 --创建触发器

 --INSERT

 CREATE TRIGGER tri_insStudent

 ON student

 AFTER INSERT

 AS

 PRINT '有新生加入了';

 GO

 

 CREATE TRIGGER tri_CheckStuName

 ON student

 AFTER INSERT,UPDATE

 AS

 IF('李四' IN(SELECT StudentName FROM inserted))

 BEGIN

  PRINT '不收李四';

  ROLLBACK TRAN;

 END

 GO

 INSERT INTO Student VALUES(444,'123','李四',0,1,'13829292','xxx','1988-1-1','q@a.a',null);

 GO

 

 --DELETE

 CREATE TRIGGER tri_DelStudent

 ON Student

 AFTER DELETE

 AS

 IF('张三' IN(SELECT StudentName FROM deleted))

 BEGIN

  PRINT '不能删除张三';

  ROLLBACK TRAN;

 END

 GO

 

 --生成毕业学生表

 SELECT *

 INTO OldStudent

 FROM Student

 WHERE 1=2;

 GO

 

 CREATE TRIGGER tri_DelStu

 ON Student

 AFTER DELETE

 AS

 INSERT INTO OldStudent SELECT * FROM deleted;

 GO

 

 DELETE FROM Student WHERE StudentName='张三';

 DELETE FROM Student WHERE StudentNO=222;

 GO

 

--UPDATE

CREATE TRIGGER tri_updStudent

ON Student

AFTER UPDATE,INSERT

AS

 DECLARE @OLDDATE DATETIME;

 DECLARE @NEWDATE DATETIME;

 SELECT @OLDDATE=BornDate FROM deleted;

 SELECT @NEWDATE=BornDate FROM inserted;

 IF(ABS(DATEDIFF(YYYY,@OLDDATE,@NEWDATE))>5)

 BEGIN

  PRINT '修改年龄不能超过5';

  ROLLBACK TRAN;

 END

GO

UPDATE Student SET BornDate='2012-1-1' WHERE StudentNo=0;