SQL Sever 第五堂课：触发器知识。

--触发器：触发器就是一种特殊的存储过程
--特殊的地方在于，触发器是通过对数据库表的操作，来引发
--存储过程是通过人为exec来执行


select *from student
create trigger Student_Insert --创建触发器
on student  --指定触发器所在的表
after insert --当执行insert操作的时候自动执行触发器,for 和after都是在操作后执行
as
    update student set sbirthdy='1999-9-9' where sno=1
go
insert into student values(7,'向立硕','男','1989-2-22',95031)



create trigger Student_Delete
on student
instead of delete --替换某个操作,用触发器的过程来替换删除的操作,不再能够删除stduent表数据
as
    update student set sbirthdy = '2015-4-29' where sno = 2
go
delete from student
select*from student
drop trigger student_delete




-----------------------------触发器格式
create trigger 触发器名
on 表名
((for/after)|instead of) 动作(insert|update|delete)
as
    存储过程内容
go


for/after :先执行操作，再执行触发器
instead of:直接替换操作
--
create trigger Student_delete2
on student
instead of delete   --把delete from student 这个操作直接替换掉
as
    delete from score where sno = 2
    delete from student where sno = 2   --有主外键关系可以执行两个表
go
delete from student 
drop trigger student_delete2--删除触发器
select*from student
select*from score


--触发器中的临时表:deleted,inserted
delete from course where cno='3-245'

create trigger Course_Delete   --创建一个的存储过程
on course                --在课程表里
instead of delete      --直接替换delete操作
as
    select *from deleted  --这是一个临时表。替换掉操作后，里面存着你要删除的那些数据
go
delete from course where cno='3-245'
--deleted是一个临时表，里面存着你要删除的那些数据、
SQL Sever 第五堂课：触发器知识。

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