触发器
步骤：打开选用的‘数据库’，然后打开‘可编程性’，就可以找到‘数据库触发器’。
是一种存储过程，只是不通过 exec 调用执行！
通过增删改语句来引发执行！
在有主外键关联时，可以把关联的信息都修改
（有主外键关联时，要先删除外键才可以删主键）
create table new
(code int ,
shu int)
go
insert into new values (1,1)
insert into new values (2,3)
insert into new values (3,4)
insert into new values (4,5)
insert into new values (5,6)
select *from new
drop table new
----------------------------------------------------
create trigger TR_new_Delete --创建并命名触发器
on new --作用于new 表
for delete--delete/insert/update --先执行删除语句,再进行插入语句
as
insert into new values (11,11)--占据删除数据的位置
insert into new values (3,4)--在新插入数据的位置
go –到此，触发器完成。
delete from new where code=3
--引发触发器语句，只能是增删改
select *from new
for/after 先运行go再运行as
--先go删除了code=3，再as添加了code=11,code=3
-- drop trigger TR_new_Delete
--------------------------------------------------
create trigger TR_new_Delete
on new
instead of delete
as
insert into new values (11,11)
go
delete from new where code=2
select * from new
--此时不执行删除语句,只执行插入语句!
instead of只运行as的语句
----------------------------------------------
alter trigger dongtaichufa
on teacher
instead of delete
as
begin
declare @Tno varchar(20)
set @Tno=(select Tno from deleted)
--deleted 表示虚拟表（go后面的delete 语句）
update teacher set Tname=‘递归‘where [email protected]
end
go
delete from teacher where Tno=‘856‘
select *from teacher
---------------------------------------------
--触发器可以处理视图，（用途：1.删除数据时备份2.操作视图，即有主外键关联时）
create trigger inserttt
on teacher
for insert
as
declare @Tno varchar(19)
set @Tno=(select Tno from inserted)
update teacher set Tsex=‘男‘where [email protected] --修改表内容
go
insert into teacher values
(‘789‘,‘集合‘,‘女‘,‘1990-09-09‘,‘教授‘,‘生物系‘)
select *from teacher
----------------------------------------------
alter table teacher disable trigger all--(或触发器名字)禁用全部
alter table teacher enable trigger all--(或触发器名字)启用全部