zoukankan      html  css  js  c++  java
  • 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;
  • 相关阅读:
    如何在域和域之间建立信任域?关键是配置域和域之间的DNS服务器
    Client Recevier 命令安装 AllUsers=1
    在XD 4.0 设置Policy
    更改linux系统中键盘设置
    如何在DNS中添加另一DNS
    CMD命令
    KMS激活OS(系统)
    谁抢了我的IP!!!~
    关于域证书的发布CA和CRL的内容 (Windows 2008 Server R2 SP1)
    XenServer假死状态
  • 原文地址:https://www.cnblogs.com/wolfocme110/p/4025846.html
Copyright © 2011-2022 走看看