no9.sql

数据库文件。对sql数据库的基本用法和创建做了介绍

create trigger deltable
on 订购表
for delete
as
declare @ordnum int
select @ordnum=count(*) from 定单明细表, deleted i where 定单明细表.定单号=i.定单号
begin
 if(@ordnum>100)/*拒绝删除*/
  begin 
  raiserror('拒绝删除!',15,1)
  rollback transaction
  end
 if(@ordnum<10)/*级联删除*/
  begin 
  delete from  定单明细表 where 定单号=(select 定单号 from deleted)
  end
/*空值删除*/
if(@ordnum>=10 and @ordnum<=100)
begin
update 定单明细表
set 定单号=null where 定单号=(select 定单号 from deleted)
end
end