create trigger coursetrigger
on course
for insert 
as 
declare @useridcount int
select @useridcount= count(*)
from inserted,teacher
where inserted.Userid=teacher.Userid;
if @UseridCount =0
 begin 
        print 'not' 
        rollback;
 end

insert into teacher
values(33,'001','zhangsan',80)

insert into course
values(34,'001','zhangsan',80)

insert into course
values(34,'002','Lisi',80)
不能插入
消息 3609，級別 16，狀態 1，第 1 行
事務在觸發器中結束。批處理已中止。


create trigger after
on student
for delete 
as 
declare @deletecount int
select @deletecount= count(*)
from deleted,sc
where deleted.sno=sc.sno;
if @deleteCount >0
 begin 
         delete sno
     from sc;
 end


DELETE
FRom student
where sno='200215121'
消息 208，級別 16，狀態 1，過程 after，第 11 行
對象名  'sno' 無效。

create trigger after
on student
for delete 
as
delete sc
 from deleted,student
 where deleted.sno=sc.sno
(當student表中有相應記錄，在sc表中也有時，那么student和sc中的記錄會一起刪，但是如果student中的相關記錄在course中無時，那么只有student受影響，如果sc表中的記錄，在student中沒有記錄時，那么兩者都是0行受影響)


create trigger del_course
on course
instead of delete
as
begin
print '你不能刪除該表的任何記錄'
end

DELETE
FRom course
where cno='1'