本文实例讲述了SQL
Server触发器和事务用法。分享给大家供大家参考,具体如下:
SQL Server 通过触发器用来保证业务逻辑和数据的完整性。在SQL
Server中,触发器是一种特殊类型的存储过程,可在执行语言事件时自动触发。SQL
Server中触发器包括三种:DML触发器、DDL触发器和登录触发器。
新增和删除触发器
- DML触发器:执行DML语句触发执行,例如操作数据表或视图的insert、update、delete语句,不包含select。
- Server触发器和事务用法示例。DDL触发器:执行DDL语句时触发执行,例如create table等语句。
- 登录触发器:在用户登录SQL Server实例创建会话时触发。
alter trigger tri_TC on t_c for INSERT,deleteasbegin set XACT_ABORT ON declare @INSERTCOUNT int; declare @DELETECOUNT int; declare @UPDATECOUNT int; set @INSERTCOUNT = (select COUNT(*) from inserted); set @DELETECOUNT = (select COUNT(*) from deleted); set @UPDATECOUNT = () if(@INSERTCOUNT 0) begin insert into t_c2 select * from inserted; end else if(@DELETECOUNT 0) begin delete t_c2 where exists(select temp.cid from deleted temp where temp.cid=t_c2.cid); endend
SQL
Server将触发器和触发它的语句放在一个可回滚事务中,如果触发器发生异常,则与该触发器相关的语句自动回滚。
更新触发器和事务
DML的功能(优点):
事务主要用在数据的保护,在多表更新时,事务保存所有事务下的更新语句就不会提交,数据也就不能更新成功
- 实现表的级联更改,实现与外键约束相似的功能(如果外键可以约束,则不推荐使用触发器)
- 防止恶意或错误的insert、update、delete操作。触发器比check约束更加强大,触发器可以引用其它数据表,执行更加复杂的限制,而check约束不能引用其它表。
- 可以获取到更改前和修改后的数据,根据差异采取措施,决定是commit,还是rollback
- 一个表支持创建多个同类型的DML触发器
alter trigger tri_TC_Update on t_c for updateasbegin declare @delcount int; set @delcount = (select count(*) from deleted); if(@delcount 0) begin begin transaction triUpdate --定义事务 declare @cname varchar(100); select @cname = cname from inserted; --保存更新后的内容 update t_c2 set cname = @cname where cid = (select cid from deleted); --更新 if (@@error 0) begin rollback transaction triUpdate; --事务回滚 end else begin commit transaction triUpdate; --事务提交 end endend
注意:有日志操作的行为才会激活触发器。例如truncate
table删除表中所有数据,并没有执行日志操作,所以不会激活delete触发器。
存储过程
澳门太阳集团,创建触发器
DML触发器分为:
- after触发器(之后触发)
- insert触发器
- update触发器
- delete触发器
- 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。
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。
if(exists(select name from sysobjects s where s.name='pro_fun' and s.type='p')) drop procedure pro_fungo create procedure pro_funas select * from tablegoexec pro_fun
创建触发器的语法:
create trigger tgr_name
on table_name
with encrypion –加密触发器
for update...
as
Transact-SQL
游标
创建insert类型触发器
insert触发器,会在inserted表中添加一条刚插入的记录。
--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;
declare @qybh varchar(10)declare cur cursor for select distinct qybh from PJ_EnterpriseInputopen curfetch next from cur into @qybhwhile @@fetch_status = 0 begin print(@qybh) fetch next from cur into @qybh endclose curdeallocate cur
创建delete类型触发器
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。
--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;
视图
创建update类型触发器
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';
alter view CreateViewas select qybh from CreateViewgo
update更新列级触发器
更新列级触发器可以用update是否判断更新列记录;
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;
定义方法
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。
语法:
create trigger tgr_name
on table_name
with encryption
instead of update...
as
T-SQL
alter function funName(@str1 varchar(10),@str2 varchar(10))returns varchar(10)asbegin declare @returnStr varchar(10) set @returnStr = 'false' if(@str1 @str2) set @returnStr = 'true' return @returnStrendselect dbo.funName(... , ...)
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;
定义表变量
显示错误信息(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;
declare @qybhTable table (id varchar(32),qybh varchar(30))insert into @qybhTableselect id,qybh from PJ_EnterpriseInputselect * from @qybhTable
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';
case when then 条件统计时的使用
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;
selectsum(case when z.watchName='注册监理工程师' then 1 else 0 end),sum(case when z.watchName='xinza' then 1 else 0 end),sum(case when z.watchName='监理员' then 1 else 0 end)from zu_corjl zright join zu_corjltemp t on t.corID=z.corID
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';
希望本文所述对大家SQL Server数据库程序设计有所帮助。
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;
本文代码来源: