--触发器:触发器就是一种特殊的存储过程,只用来“增删改” --触发器特殊的地方就在于,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,还可以写成after,for和after都是在操作后执行 for Insert --当执行insert操作的时候自动执行触发器 as update Student set sbirthday=‘1980-08-20‘where Sno=110 go insert into Student values(110,‘王二小‘,‘男‘,‘1979-09-02‘,95033) create trigger Student_Delete --创建触发器 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,不在能够删除student表 as update Student set sbirthday=‘1980-08-20‘where Sno=110 go delete from Student drop trigger Student_Delete --删除触发器 create trigger Student_Delete2 --删除某一条数据 on Student instead of delete as delete from Score where Sno=105 delete from Student where Sno=105 go delete from Student delete from Course where Cno=‘3-105‘ create trigger Course_Delete --course表中的cno有主外键关系--deleted触发器中的临时表 on Course instead of delete as select *from deleted --deleted相当于虚拟的临时表,里面存着你要删除的那些数据 go delete from Course where Cno=‘3-105‘ drop trigger Course_Delete --删除触发器 --一次性删除Course表数据,实用触发器替换删除操作,线删除外键表相关数据,再删除主键表course表相关数据 create trigger Course_Delete2--只能删除一行,要是删除多行由于赋值的问题遍历后只把最后一个数赋值执行,所以只删除了最后一行 on Course instead of delete as declare @cno varchar(20) select @cno = cno delete from score where cno=@cno delete from course where cno=@cno go create trigger Course_Delete4--一条一条删除多行 on Course instead of delete as delete from score where cno in (selete cno from deleted) delete from course where cno in (selete cno from deleted) go create trigger Course_Delete3 on Course instead of delete as declare @count int select @coount = count(*) from deleted if @count==1 --执行删除一行的操作 begin declare @cno varchar(20) select @cno = cno delete from score where cno=@cno delete from course where cno=@cno end if @count>1 --循环遍历每一行,分别执行删除一行的操作 begin delete from score where cno in (selete cno from deleted) delete from course where cno in (selete cno from deleted) end go drop table Scorebak drop trigger Score_Delete --删除前先备份数据到备份表之后再删除 create table Scorebak ( ids int identity(1,1) primary key, sno varchar(50), cno varchar(50), degree decimal(4,1), dayetime datetime ) create trigger Score_Delete --备份删除 on Score instead of delete as declare @count int select @count = count(*) from deleted declare @i int set @i = 0 while @i<@count --循环遍历deleted临时表的数据,然后转移到Scorebak begin declare @sno varchar(20) declare @cno varchar(20) declare @degree decimal(4,1) select top 1 @sno=sno,@cno=cno,@degree=degree from deleted where sno not in (select top (@i) sno from deleted) or cno not in(select top (@i) cno from deleted) --or degree not in (select top(@i) degree from score)--两条就能确定时,不用全写,这道题不用写degree not in,分页查询每一行 insert into Scorebak values(@sno,@cno,@degree,getdate()) delete from score where [email protected] and cno=@cno set @[email protected]+1 end go select *from Scorebak select *from Score delete from Score where Cno=‘3-105‘
时间: 2024-09-28 15:39:20