【触发器】数据库_触发器实例
數據庫觸發器案例
一、課堂演示案例
例一：創建一個簡單的insert觸發器
先創建一個數據庫備用
create database sampledb
go
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use sampledb
go
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在新創建的庫中創建一個表備用
create table aa
(
?a int,
?b int
)
go
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在新創建的表上創建一個insert觸發器
use sampledb
go
?
if exists(select name from sysobjects where name ='tr_intoa' and type='tr')
drop trigger tr_intoa
go
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create trigger tr_intoa on aa
for insert
as
print 'success inserted one row!'
?
查看這個觸發器的定義文本
sp_helptext checkpubdate
?
查看這個觸發器的信息
sp_help checkpubdate
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驗證這個觸發器的工作情況
insert into aa values (1,2)
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例二：創建一個觸發器監視insert操作，若插入的記錄中版權費超過30，則提示用戶，并回滾此操作。
use pubs
go
?
if exists(select name from sysobjects where name ='CheckRoyalty' and type='tr')
drop trigger CheckRoyalty
go
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create trigger checkroyalty
on roysched
for insert as
if (select royalty from inserted) > 30
begin
print 'royaltytrigger：版權費不能超過?30'
?print '請將版權費修改為小于?30 的值'
?rollback transaction
end
?
insert into roysched values ('BU1032',2,5,90)
?
select * from roysched where title_id='BU1032'
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例三：創建一個觸發器監視insert操作，若插入的記錄中出版日期小于當前日期，則提示用戶，并回滾此操作。
use pubs
go
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if exists(select name from sysobjects where name ='checkpubdate' and type='tr')
drop trigger checkpubdate
go
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create trigger checkpubdate
on titles
for insert as
if (select pubdate from inserted) < getdate()
begin
??select * from inserted ??--查看內存表中的數據
??print '出版日期小于當前日期'
??rollback transaction
end
?
觸發器示例測試
insert into titles(title_id,title,type,pubdate)
values('SW0001','test book','business','1990-1-1')
?
select * from inserted
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例四：列級update觸發器示例
use pubs
go
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if exists(select name from sysobjects where name ='NoUpdatePayterms' and type='tr')
drop trigger NoUpdatePayterms
go
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CREATE TRIGGER NoUpdatePayterms
ON sales
FOR UPDATE AS
IF UPDATE (payterms)
BEGIN
? PRINT '不能修改訂單的付費條款'
ROLLBACK TRANSACTION
END
?
測試觸發器的工作情況
update sales set qty=8
where stor_id='6380' and
??????ord_num='6871' and
??????title_id='BU1032'
?
update sales set payterms='aa'
where stor_id='6380' and
??????ord_num='6871' and
??????title_id='BU1032'
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例五：表級update觸發器實例
use pubs
go
?
if exists(select name from sysobjects where name ='NoUpdateDiscount' and type='tr')
drop trigger NoUpdateDiscount
go
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create trigger NoUpdateDiscount
on discounts
for update as
?
if (select discount from inserted) > 12
begin
????select * from inserted ??--查看內存表中的數據
????select * from deleted ??--查看內存表中的數據
??print '不能指定大于 12% 的折扣'
??rollback transaction
end
?
表級 UPDATE 觸發器測試
update discounts ?
set discount = 20 ?
where stor_id = '8042'
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例六：列級update 觸發器示例
use ?northwind
go
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建立登記修改人帳號的表
create table who_change
(
?change_date datetime,
?change_column varchar(50),
?who varchar(50)
)
go
?
建立觸發器
use ?northwind
go
?
if exists(select name from sysobjects where name ='tr_orderdetail_insupd' and type='tr')
drop trigger tr_orderdetail_insupd
go
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create trigger tr_orderdetail_insupd
on
[order details]
for update
as
if update (unitprice)
begin
??insert who_change
??values (getdate(),'unitprice updated',user_name())
end
else if update (Quantity)
??begin
????insert who_change values(getdate(),'quantity updated',user_name()) ???
??end
else if update(discount)
begin
??insert who_change values (getdate(),'discount updated',user_name())
end
go
?
測試觸發器的工作情況
update [order details] set unitprice=2 where orderid=10248 and productid=1
update [order details] set Quantity=4 where orderid=10248 and productid=1
update [order details] set discount=0 where orderid=10248 and productid=1
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例七：觸發器只能在當前數據庫中創建。 但是，觸發器可以引用其他數據庫中的對象。(示例)
use sampledb
go
?
創建表test備用
create table test
(
?aa int,
?bb int
)
go
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向test表中插入一些數據備用
insert into test values (1001,0)
insert into test values (1002,0)
insert into test values (1003,0)
?
創建另一個庫備用
create database testdb
go
?
use testdb
go
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在庫testdb中再創建一個表備用
create table test_11
(
?aa int,
?bb int
)
go
?
在testdb庫中的表test_11上創建一個insert觸發器
use testdb
go
?
if exists(select name from sysobjects where name ='tri_test' and type='tr')
drop trigger tri_test
go
?
create trigger tri_test on test_11
for insert
as
??update sampledb.dbo.test
??set bb=bb+(select bb from inserted)
??where aa= (select aa from inserted)
?
測試觸發器的工作情況
insert into test_11 values (1002,2)
?
insert into test_11 values (1001,1)
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例八：DELETE 觸發器示例
use testdb
go
?
if exists(select name from sysobjects where name ='NoDelete9901' and type='tr')
drop trigger NoDelete9901
go
?
create trigger NoDelete9901
on pub_info
for delete AS
if (select pub_id from deleted) = '9901'
begin
??print '不能刪除出版商 9901 的詳細信息'
??rollback transaction
end
?
DELETE 觸發器示例測試
delete pub_info
where pub_id = '9901'
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例九：視圖上的 INSTEAD OF 觸發器示例
use pubs
go
?
select * into bak_employee from employee
select * into bak_publishers from publishers
?
create view Emp_pub
as
select emp_id, lname, job_id, pub_name
from bak_employee e, bak_publishers p
where e.pub_id = p.pub_id
?
create trigger del_emp
on Emp_pub
instead of delete
as
??select * from deleted ??--查看內存表中的數據
??delete bak_publishers
??where emp_id in
(select emp_id from deleted)
?
視圖上的 INSTEAD OF 觸發器示例測試
delete Emp_pub
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例十：表上的INSTEAD OF 觸發器示例
use pubs
go
?
if exists(select name from sysobjects where name ='tri_deltitle' and type='tr')
drop trigger tri_deltitle
go
?
create trigger tri_deltitle on titles
instead of delete
as
print '不允許刪除！'
?
delete from titles where title_id='BU1032'
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例十一：禁用觸發器嵌套
exec sp_configure 'nested trigger', 0
?
例十二：啟用觸發器嵌套
exec sp_configure 'nested trigger', 1
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例十三：觸發器嵌套示例
?
use sampledb
go
建立觸發器
create table testa
(
???a_id char(1),
???a_name char(2)
)
insert into testa values('1','1')
insert into testa values('2','2')
insert into testa values('3','3')
?
create table testb
(
???b_id char(1),
???b_name char(2)
)
insert into testb values('1','1')
insert into testb values('2','2')
insert into testb values('3','3')
?
create table testc
(
???c_id char(1),
???c_name char(2)
)
insert into testc values('1','1')
insert into testc values('2','2')
insert into testc values('3','3')
?
觸發器嵌套示例(1)
create trigger del_testa
on testa
instead of delete
as
??delete testb
??where b_id in
(select a_id from deleted)
?
create trigger del_testb
on testb
instead of delete
as
??delete testc
??where c_id in
(select b_id from deleted)
?
觸發器嵌套示例測試(1)
delete testa where a_id = '1'
?
-- drop trigger del_testa2
-- drop trigger del_testb2
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觸發器嵌套示例(2)
create trigger del_testa2
on testa
for delete
as
??delete testb
??where b_id in
(select a_id from deleted)
?
create trigger del_testb2
on testb
for delete
as
?delete testc
??where c_id in
(select b_id from deleted)
?
觸發器嵌套示例測試(1)
delete testa where a_id = '1'
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例十四：觸發器綜合應用
創建觸發器
use northwind
if exists(select name from sysobjects where name ='tr_product_update' and type='tr')
drop trigger tr_product_update
go
?
use ?northwind
go
?
create trigger tr_product_update on products
for update
as
declare @msg varchar(100)
select @msg = str(@@rowcount)+'employees updated by this statement'
print @msg
return
go
?
管理觸發器
use ?northwind
go
?
sp_helptrigger products,delete
?
inerted和deleted表實現級聯修改多數據表的觸發器
use ?northwind
go
?
create trigger tr_suppliers_del
on suppliers
for delete
as
if @@rowcount=0
??return
delete products from deleted d,suppliers s
where d.supplierid=s.supplierid
if @@error != 0
begin
??rollback tran
??return
end
return
go
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例十五：列級觸發器應用
列級觸發器 在通常情況下，用戶對表所作的修改都只局限在表中的某些列上，而且，用戶經常需要判斷在某些列上的數據是否發生了修改，并在數據被修改時作出相應的反應。這種形式的觸發器，被稱為列級觸發器。列級觸發器主要
針對某些列實施監控。
use ?northwind
go
?
建立登記修改人帳號的表
create table who_change
(
?change_date datetime,
?change_column varchar(50),
?who varchar(50)
)
go
?
建立觸發器
create trigger tr_orderdetail_insupd
on
[order details]
for insert,uodate
as
if update (unitprice)
begin
??insert who_change
??values (getdate(),'unitprice updated',user_name())
end
else if update (Quantity)
??begin
????insert who_change values(getdate(),'quantity updated',user_name()) ???
??end
else if update(discount)
begin
??insert who_change values (getdate(),'discount updated',user_name())
end
go
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