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觸發器是一種特別類型的存儲進程，它分歧於之前的我們引見的存儲進程。觸發器重要是經由過程事宜停止觸發被主動挪用履行的。而存儲進程可以經由過程存儲進程的稱號被挪用。
Ø 甚麼是觸發器
觸發器對表停止拔出、更新、刪除的時刻會主動履行的特別存儲進程。觸發器普通用在check束縛加倍龐雜的束縛下面。觸發器和通俗的存儲進程的差別是：觸發器是當對某一個表停止操作。諸如：update、insert、delete這些操作的時刻，體系會主動挪用履行該表上對應的觸發器。SQL Server 2005中觸發器可以分為兩類：DML觸發器和DDL觸發器，個中DDL觸發器它們會影響多種數據界說說話語句而激起，這些語句有create、alter、drop語句。
DML觸發器分為：
1、 after觸發器（以後觸發）
a、 insert觸發器
b、 update觸發器
c、 delete觸發器
2、 instead of 觸發器 （之前觸發）
個中after觸發器請求只要履行某一操作insert、update、delete以後觸發器才被觸發，且只能界說在表上。而instead of觸發器表現其實不履行其界說的操作（insert、update、delete）而僅是履行觸發器自己。既可以在表上界說instead of觸發器，也能夠在視圖上界說。
觸發器有兩個特別的表：拔出表（instered表）和刪除表（deleted表）。這兩張是邏輯表也是虛表。有體系在內存中創立者兩張表，不會存儲在數據庫中。並且兩張表的都是只讀的，只能讀取數據而不克不及修正數據。這兩張表的成果老是與被改觸發器運用的表的構造雷同。當觸發器完成任務後，這兩張表就會被刪除。Inserted表的數據是拔出或是修正後的數據，而deleted表的數據是更新前的或是刪除的數據。
對表的操作
Inserted邏輯表
Deleted邏輯表
增長記載（insert）
寄存增長的記載
無
刪除記載（delete）
無
寄存被刪除的記載
修正記載（update）
寄存更新後的記載
寄存更新前的記載
Update數據的時刻就是先刪除表記載，然後增長一筆記錄。如許在inserted和deleted表就都有update後的數據記載了。留意的是：觸發器自己就是一個事務，所以在觸發器外面可以對修正數據停止一些特別的檢討。假如不知足可以應用事務回滾，撤消操作。
Ø 創立觸發器
語法
create trigger tgr_name
on table_name
with encrypion –加密觸發器
for update...
as
Transact-SQL
# 創立insert類型觸發器
--創立insert拔出類型觸發器
if (object_id('tgr_classes_insert', 'tr') is not null)
drop trigger tgr_classes_insert
go
create trigger tgr_classes_insert
on classes
for insert --拔出觸發
as
--界說變量
declare @id int, @name varchar(20), @temp int;
--在inserted表中查詢曾經拔出記載信息
select @id = id, @name = name from inserted;
set @name = @name + convert(varchar, @id);
set @temp = @id / 2;
insert into student values(@name, 18 + @id, @temp, @id);
print '添加先生勝利！';
go
--拔出數據
insert into classes values('5班', getDate());
--查詢數據
select * from classes;
select * from student order by id;
insert觸發器，會在inserted表中添加一條剛拔出的記載。
# 創立delete類型觸發器
--delete刪除類型觸發器
if (object_id('tgr_classes_delete', 'TR') is not null)
drop trigger tgr_classes_delete
go
create trigger tgr_classes_delete
on classes
for delete --刪除觸發
as
print '備份數據中……';
if (object_id('classesBackup', 'U') is not null)
--存在classesBackup，直接拔出數據
insert into classesBackup select name, createDate from deleted;
else
--不存在classesBackup創立再拔出
select * into classesBackup from deleted;
print '備份數據勝利！';
go
--
--不顯示影響行數
--set nocount on;
delete classes where name = '5班';
--查詢數據
select * from classes;
select * from classesBackup;
delete觸發器會在刪除數據的時刻，將適才刪除的數據保留在deleted表中。
# 創立update類型觸發器
--update更新類型觸發器
if (object_id('tgr_classes_update', 'TR') is not null)
drop trigger tgr_classes_update
go
create trigger tgr_classes_update
on classes
for update
as
declare @oldName varchar(20), @newName varchar(20);
--更新前的數據
select @oldName = name from deleted;
if (exists (select * from student where name like '%'+ @oldName + '%'))
begin
--更新後的數據
select @newName = name from inserted;
update student set name = replace(name, @oldName, @newName) where name like '%'+ @oldName + '%';
print '級聯修正數據勝利！';
end
else
print '無需修正student表！';
go
--查詢數據
select * from student order by id;
select * from classes;
update classes set name = '五班' where name = '5班';
update觸發器會在更新數據後，將更新前的數據保留在deleted表中，更新後的數據保留在inserted表中。
# update更新列級觸發器
if (object_id('tgr_classes_update_column', 'TR') is not null)
drop trigger tgr_classes_update_column
go
create trigger tgr_classes_update_column
on classes
for update
as
--列級觸發器：能否更新了班級創立時光
if (update(createDate))
begin
raisError('體系提醒：班級創立時光不克不及修正！', 16, 11);
rollback tran;
end
go
--測試
select * from student order by id;
select * from classes;
update classes set createDate = getDate() where id = 3;
update classes set name = '四班' where id = 7;
更新列級觸發器可以用update能否斷定更新列記載；
# instead of類型觸發器
instead of觸發器表現其實不履行其界說的操作（insert、update、delete）而僅是履行觸發器自己的內容。
創立語法
create trigger tgr_name
on table_name
with encryption
instead of update...
as
T-SQL
# 創立instead of觸發器
if (object_id('tgr_classes_inteadOf', 'TR') is not null)
drop trigger tgr_classes_inteadOf
go
create trigger tgr_classes_inteadOf
on classes
instead of delete/*, update, insert*/
as
declare @id int, @name varchar(20);
--查詢被刪除的信息，病賦值
select @id = id, @name = name from deleted;
print 'id: ' + convert(varchar, @id) + ', name: ' + @name;
--先刪除student的信息
delete student where cid = @id;
--再刪除classes的信息
delete classes where id = @id;
print '刪除[ id: ' + convert(varchar, @id) + ', name: ' + @name + ' ] 的信息勝利！';
go
--test
select * from student order by id;
select * from classes;
delete classes where id = 7;
# 顯示自界說新聞raiserror
if (object_id('tgr_message', 'TR') is not null)
drop trigger tgr_message
go
create trigger tgr_message
on student
after insert, update
as raisError('tgr_message觸發器被觸發', 16, 10);
go
--test
insert into student values('lily', 22, 1, 7);
update student set sex = 0 where name = 'lucy';
select * from student order by id;
# 修正觸發器
alter trigger tgr_message
on student
after delete
as raisError('tgr_message觸發器被觸發', 16, 10);
go
--test
delete from student where name = 'lucy';
# 啟用、禁用觸發器
--禁用觸發器
disable trigger tgr_message on student;
--啟用觸發器
enable trigger tgr_message on student;
# 查詢創立的觸發器信息
--查詢已存在的觸發器
select * from sys.triggers;
select * from sys.objects where type = 'TR';
--檢查觸發器觸發事宜
select te.* from sys.trigger_events te join sys.triggers t
on t.object_id = te.object_id
where t.parent_class = 0 and t.name = 'tgr_valid_data';
--檢查創立觸發器語句
exec sp_helptext 'tgr_message';
# 示例，驗證拔出數據
if ((object_id('tgr_valid_data', 'TR') is not null))
drop trigger tgr_valid_data
go
create trigger tgr_valid_data
on student
after insert
as
declare @age int,
@name varchar(20);
select @name = s.name, @age = s.age from inserted s;
if (@age < 18)
begin
raisError('拔出新數據的age有成績', 16, 1);
rollback tran;
end
go
--test
insert into student values('forest', 2, 0, 7);
insert into student values('forest', 22, 0, 7);
select * from student order by id;
# 示例，操作日記
if (object_id('log', 'U') is not null)
drop table log
go
create table log(
id int identity(1, 1) primary key,
action varchar(20),
createDate datetime default getDate()
)
go
if (exists (select * from sys.objects where name = 'tgr_student_log'))
drop trigger tgr_student_log
go
create trigger tgr_student_log
on student
after insert, update, delete
as
if ((exists (select 1 from inserted)) and (exists (select 1 from deleted)))
begin
insert into log(action) values('updated');
end
else if (exists (select 1 from inserted) and not exists (select 1 from deleted))
begin
insert into log(action) values('inserted');
end
else if (not exists (select 1 from inserted) and exists (select 1 from deleted))
begin
insert into log(action) values('deleted');
end
go
--test
insert into student values('king', 22, 1, 7);
update student set sex = 0 where name = 'king';
delete student where name = 'king';
select * from log;
select * from student order by id;
