数据库触发器

create trigger user_Delete//创建一个名为user_Delete的触发器
                on User  //针对于User表
                for Delete   //执行删除操作
                as //执行完后要干的事情
                Select* from User  //查询user表



               create trigger user_Delete//创建一个名为user_Delete的触发器
                on User  //针对于User表
               //如果执行的是Delete事件将会被Select * from deleted 语句代替
                instead of Delete
                as
                Select* from deleted  //（查看你要删除的数据）



               create trigger user_Delete//创建一个名为user_Delete的触发器
                on User  //针对于User表
                instead of Delete
                as
                declare @a nvarchar(200);//声明一个字符串类型的a的变量
                Select @a = ids from deleted;//获取要删除的数据的ids列并赋值给a
            if @a = 5;//如果a=5
            begin
                select ‘不能删除‘
                end//不等于5
                else
            begin
            delete  from users where ids=@a
                end