dianlanren 发表于 2015-8-24 20:21:15

SQL SERVER触发器用法详解

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)存放增加的记录无
删除记录(delete)无存放被删除的记录
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--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班';
   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 = 7;

   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raiserrorif (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;

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