create tigger f on student for update as begin update a set student_id=xx from student_course a,instered i where a.student_id=i.student_id end
你非要更新那就要先删除student_course的相应记录,然后修改student表 删除应该可以使用事前触发器instead of
你这个不是用触发器,是用级联./* 标题:两表通过字段关联进行级联删除。 作者:爱新觉罗·毓华(十八年风雨,守得冰山雪莲花开) 时间:2008-11-20 地点:广东深圳 */create table ta(id int not null) create table tb(id int , aid int) insert into ta values(1) insert into ta values(2) insert into tb values(1 , 1) insert into tb values(2 , 2) insert into tb values(3 , 1) go--一、查看原始数据 --ta表的原始数据 select * from ta /* id ----------- 1 2 */ --tb表的原始数据 select * from tb /* id aid ----------- ----------- 1 1 2 2 3 1 */--二、看看没有创建级联删除时的情况(删除ta表id=1的数据,看看是否影响tb表) delete from ta where id = 1 select * from ta /* id ----------- 2 */ select * from tb /* id aid ----------- ----------- 1 1 2 2 3 1 */--三、恢复原始数据,创建级联删除,删除ta表id=1的数据,看看是否影响tb表 insert into ta values(1) --为ta创建主健 alter table ta add constraint pk_ta_id primary key (id) go --为tb创建外健,并指定级联删除 alter table tb add constraint fk_tb_aid foreign key (aid) references ta(id) on delete cascade go delete from ta where id = 1 select * from ta /* id ----------- 2 */ select * from tb /* id aid ----------- ----------- 2 2 */--删除级联约束 alter table tb drop constraint fk_tb_aid go --删除测试表 drop table ta , tb go
不需要先删除student_course相应的id吗?
如果每次更新只更新一个(如果一次更新多个没办法找对应关系,特别是存在同姓名的情况下)create trigger tri_stu_update on student for update as declare @oldid varchar(20),@newid varchar(20) select @oldid=ltrim(student_id) from deleted; select @newid=ltrim(student_id) from inserted; update student_course set student_id=@newid where student_id=@oldid end
for update
as
begin
update a set student_id=xx from student_course a,instered i where a.student_id=i.student_id
end
删除应该可以使用事前触发器instead of
标题:两表通过字段关联进行级联删除。
作者:爱新觉罗·毓华(十八年风雨,守得冰山雪莲花开)
时间:2008-11-20
地点:广东深圳
*/create table ta(id int not null)
create table tb(id int , aid int)
insert into ta values(1)
insert into ta values(2)
insert into tb values(1 , 1)
insert into tb values(2 , 2)
insert into tb values(3 , 1)
go--一、查看原始数据
--ta表的原始数据
select * from ta
/*
id
-----------
1
2
*/
--tb表的原始数据
select * from tb
/*
id aid
----------- -----------
1 1
2 2
3 1
*/--二、看看没有创建级联删除时的情况(删除ta表id=1的数据,看看是否影响tb表)
delete from ta where id = 1
select * from ta
/*
id
-----------
2
*/
select * from tb
/*
id aid
----------- -----------
1 1
2 2
3 1
*/--三、恢复原始数据,创建级联删除,删除ta表id=1的数据,看看是否影响tb表
insert into ta values(1)
--为ta创建主健
alter table ta add constraint pk_ta_id primary key (id)
go
--为tb创建外健,并指定级联删除
alter table tb add constraint fk_tb_aid foreign key (aid) references ta(id) on delete cascade
go
delete from ta where id = 1
select * from ta
/*
id
-----------
2
*/
select * from tb
/*
id aid
----------- -----------
2 2
*/--删除级联约束
alter table tb drop constraint fk_tb_aid
go
--删除测试表
drop table ta , tb
go
on student
for update
as
declare @oldid varchar(20),@newid varchar(20)
select @oldid=ltrim(student_id) from deleted;
select @newid=ltrim(student_id) from inserted;
update student_course
set student_id=@newid
where student_id=@oldid
end