join inserted i on i.sno=sc.sno)<6 insert into sc
select* from inserted
任务4：限制不能删除有人选的课程。 后触发器：
create trigger abs_tal on sc after delete as
if exists (select * from deleted d join sc on d.sno=sc.sno where sc.sno=d.sno ) begin
print'不能删除有人选的课程' rollback end
前触发器：
create trigger abs_talle on sc instead of delete as
if not exists (select * from deleted d join sc on d.sno=sc.sno where sc.sno=d.sno ) delete from sc
where cno in(select cno from deleted)
四、实验中遇到的问题及解决（或未解决）的方案