SQL Server 触发器

触发器是一种特殊类型的存储过程,它不同于之前的我们介绍的存储过程。触发器主要是通过事件进行触发被自动调用执行的。而存储过程可以通过存储过程的名称被调用。

Ø 什么是触发器

    触发器对表进行插入、更新、删除的时候会自动执行的特殊存储过程。触发器一般用在check约束更加复杂的约束上面。触发器和普通的存储过程的区别是:触发器是当对某一个表进行操作。诸如:update、insert、delete这些操作的时候,系统会自动调用执行该表上对应的触发器。SQL Server 2005中触发器可以分为两类:DML触发器和DDL触发器,其中DDL触发器它们会影响多种数据定义语言语句而激发,这些语句有create、alter、drop语句。

    DML触发器分为:

    1、 after触发器(之后触发)

        a、 insert触发器

        b、 update触发器

        c、 delete触发器

    2、 instead of 触发器 (之前触发)

    其中after触发器要求只有执行某一操作insert、update、delete之后触发器才被触发,且只能定义在表上。而instead of触发器表示并不执行其定义的操作(insert、update、delete)而仅是执行触发器本身。既可以在表上定义instead of触发器,也可以在视图上定义。

    触发器有两个特殊的表:插入表(instered表)和删除表(deleted表)。这两张是逻辑表也是虚表。有系统在内存中创建者两张表,不会存储在数据库中。而且两张表的都是只读的,只能读取数据而不能修改数据。这两张表的结果总是与被改触发器应用的表的结构相同。当触发器完成工作后,这两张表就会被删除。Inserted表的数据是插入或是修改后的数据,而deleted表的数据是更新前的或是删除的数据。

对表的操作

Inserted逻辑表

Deleted逻辑表

增加记录(insert)

存放增加的记录

删除记录(delete)

存放被删除的记录

修改记录(update)

存放更新后的记录

存放更新前的记录

    Update数据的时候就是先删除表记录,然后增加一条记录。这样在inserted和deleted表就都有update后的数据记录了。注意的是:触发器本身就是一个事务,所以在触发器里面可以对修改数据进行一些特殊的检查。如果不满足可以利用事务回滚,撤销操作。

Ø 创建触发器

    语法

Create Trigger tgr_name
On table_name
   With encrypion –加密触发器
For  Update...
As
    Transact -Sql

# 创建insert类型触发器

/************************************************************
 * Code formatted by SoftTree SQL Assistant ?v6.0.70
 * Time: 2014-10-15 10:42:34
 ************************************************************/

--创建insert插入类型触发器
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--插入触发
As
    --定义变量
    Declare @id Int, @name Varchar(20), @temp Int;
    --在inserted表中查询已经插入记录信息
    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 '添加学生成功!';
Go
--插入数据
Insert Into classes
Values
  (
    '5班', Getdate()
  );
--查询数据
Select *
From   classes;
Select *
From   student
Order By
       id;

insert触发器,会在inserted表中添加一条刚插入的记录。

# 创建delete类型触发器

--delete删除类型触发器
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--删除触发
As
    Print '备份数据中……';    
    If (Object_id('classesBackup', 'U') Is Not Null)
        --存在classesBackup,直接插入数据
        Insert Into classesBackup
        Select Name, createDate
        From   Deleted;
    Else
    --不存在classesBackup创建再插入
    Select * Into classesBackup
    From   Deleted;
    Print '备份数据成功!';
Go
--
--不显示影响行数
--set nocount on;
Delete classes
Where  Name = '5班';
--查询数据
Select *
From   classes;
Select *
From   classesBackup;

delete触发器会在删除数据的时候,将刚才删除的数据保存在deleted表中。

# 创建update类型触发器

--update更新类型触发器
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);
    --更新前的数据
    Select @oldName = Name
    From   Deleted;
    If (
           Exists (
               Select *
               From   student
               Where  Name Like '%' + @oldName + '%'
           )
       )
    Begin
        --更新后的数据
        Select @newName = Name
        From   Inserted;
        Update student
        Set    Name = Replace(Name, @oldName, @newName)
        Where  Name Like '%' + @oldName + '%';
        Print '级联修改数据成功!';
    End
    Else
        Print '无需修改student表!';
Go
--查询数据
Select *
From   student
Order By
       id;
Select *
From   classes;
Update classes
Set    Name  = '五班'
Where  Name  = '5?

update触发器会在更新数据后,将更新前的数据保存在deleted表中,更新后的数据保存在inserted表中。

# update更新列级触发器

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
    --列级触发器:是否更新了班级创建时间
    If (Update(createDate))
    Begin
        Raiserror('系统提示:班级创建时间不能修改!', 16, 11);
        Rollback Tran;
    End
Go
--测试
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    = 

 更新列级触发器可以用update是否判断更新列记录;

# instead of类型触发器

       instead of触发器表示并不执行其定义的操作(insert、update、delete)而仅是执行触发器本身的内容。

       创建语法

Create Trigger tgr_name
On table_name
   With Encryption
   Instead Of Update...
As
    T -Sql

# 创建instead of触发器

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);
    --查询被删除的信息,病赋值
    select @id = id, @name = name from deleted;
    print 'id: ' + convert(varchar, @id) + ', name: ' + @name;
    --先删除student的信息
    delete student where cid = @id;
    --再删除classes的信息
    delete classes where id = @id;
    print '删除[ id: ' + convert(varchar, @id) + ', name: ' + @name + ' ] 的信息成功!';
go
--test
select * from student order by id;
select * from classes;
delete classes where id = 7;

# 显示自定义消息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触发器被触发', 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;

# 修改触发器

alter trigger tgr_message
on student
after delete
as raisError('tgr_message触发器被触发', 16, 10);
go
--test
delete from student where name = 'lucy';

# 启用、禁用触发器

--禁用触发器
disable trigger tgr_message on student;
--启用触发器
enable trigger tgr_message on student;

# 查询创建的触发器信息

--查询已存在的触发器
select * from sys.triggers;
select * from sys.objects where type = 'TR';

--查看触发器触发事件
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';

--查看创建触发器语句
exec sp_helptext 'tgr_message';

# 示例,验证插入数据

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('插入新数据的age有问题', 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,操作日志

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;
原文地址:https://www.cnblogs.com/wolfocme110/p/4025846.html