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trigger

时间:2015-01-06 20:02:20      阅读:248      评论:0      收藏:0      [点我收藏+]

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trigger

 

一、类型:  

  DML触发器:insert、update、delete  

  替代触发器:针对视图  

  系统触发器:针对系统事件

 

二、触发频率:  

  语句级(statement):当触发事件发生时,该触发器只执行一次;  

  行级(row):当触发事件发生时,针对会受到影响的每一行数据,触发器都会执行一次;

 

三、注意:  

  一个表最多只能有12个触发器,且相互不可矛盾、重复;  

  单个触发器最多为32KB;  

  触发器中不能包含事物控制语句(commit,rollback,savepoint);且其中调用的过程和函数语句中也不能有事物控制语言;  

  当触发器中有 “for each row” 选项时,则表示为语句级触发器;         

    缺省 “for each row” 选项时,before 和 after 触发器为语句级触发器,instead of 触发器为行触发器;  

  系统事件:         

    startup           启动数据库实例之后         

    shutdown          关闭数据库实例之前         

    servererror       出现错误之后         

    logon             连接之后         

    logoff            断开连接之前         

    create                    

    drop         

    alter         

    ddl         

    grant         

    revoke         

    rename         

    audit/noaudit                             

 

四、语法:

create or replace trigger 触发器名 出发时间 触发事件       

  on 表名 [for each row]       

  [when condition]       

  [pl/sql]       

 

五、实例: 

5.1、简单 after update

create table test_dept as select * from test_dept;
create or replace trigger test_trigger01 
       after update  
       on test_dept for each row
begin
       dbms_output.put_line(:old.deptno||=++++++=||:new.deptno);
end;

update test_dept set b=11111 where a=a;
commit;

drop trigger test_trigger01;
drop table test_dept;

 

5.2、deleting,updating,inserting应用,将某表中的数据修改记录插入到另一张表中

 --deleting   只有:old
 --inserting  只有:new
 --updating   :old和:new都有

create table test_dept as select * from dept;
create table test_dept_log as select a.*,删除 as flag,sysdate as time_ from dept a where 1=2;

create or replace trigger test_trigger02 
       after update or delete or insert  
       on test_dept for each row
begin
       case 
         when updating then 
              insert into test_dept_log values(:old.deptno,:old.dname,:old.loc,修改,sysdate);
         when inserting then
              insert into test_dept_log values(:new.deptno,:new.dname,:new.loc,插入,sysdate);
         when deleting then 
              insert into test_dept_log values(:old.deptno,:old.dname,:old.loc,删除,sysdate);
       end case;
       /*--也可以写成:
         if updating then 
              insert into test_dept_log values(:old.deptno,:old.dname,:old.loc,‘修改‘,sysdate);
         elsif inserting then   --【注意是elsif,而不是elseif】
              insert into test_dept_log values(:new.deptno,:new.dname,:new.loc,‘插入‘,sysdate);
         elsif deleting then 
              insert into test_dept_log values(:old.deptno,:old.dname,:old.loc,‘删除‘,sysdate);
         end if;
       */
end;

update test_dept set loc=test where deptno=20;       
insert into test_dept values(50,wer,wer); 
delete from test_dept where deptno=50;   
select * from test_dept_log;
select * from test_dept;  

drop table test_dept;       
drop table test_dept_log;
drop trigger test_trigger02;

5.3、当前用户不是scott,则不允许修改

create table test_dept as select * from dept;
create or replace trigger test_trigger03 
       before update or insert or delete 
       on test_dept
       for each row
--when ((select count(*) from dual where user)=‘SCOTT‘>0)
when (upper(user)<>SCOTT)
declare tt varchar2(20);
begin
  select user into tt from dual;
  raise_application_error(-20001,当前用户是||tt||,没有操作权限!);
end;

update test_dept set loc=test_ where deptno=20;
select * from test_dept;

drop table test_dept;
drop trigger test_trigger03;

5.4、instead of触发器,建立在视图上,且该视图没有指定 with check option 选项;

create table test01(
       a number(10),
       b number(10),
       c number(10));
create table test02 as 
       select * from test01 where 1=2;
create view test_view01 as 
       select a.a,b.b from test01 a,test02 b where a.a=b.a and a.b=b.b;

create or replace trigger test_trigger04 
       instead of insert
       on test_view01
       for each row
begin
       --raise_application_error(-20001,‘视图不可插入数据!‘);
       insert into test01 values (:new.a,null,null);
       insert into test02 values (null,:new.b,null);
end;

insert into test_view01 values(1,1);
insert into test_view01 
       select 2,2 from dual
       union all
       select 3,3 from dual;
select * from test01;
select * from test02;

drop view test_view01;
drop trigger test_trigger04;
drop table test02;
drop table test01;

5.5、将用户登陆和登出记录到数据表
--创建系统触发器,用户需要有administer database trigger权限
--以下操作在sys用户下可成功完成

create table test_login(
       event_ varchar2(10),
       user_ varchar2(20),
       address_ varchar2(100),
       date_ date
       );
create or replace trigger test_trigger05 
       after logon on database
begin
       insert into test_login values(登陆,user,ora_client_ip_address,sysdate);
end;        

create or replace trigger test_trigger06 
       before logoff on database
begin
       insert into test_login values(登出,user,ora_client_ip_address,sysdate);
end; 

drop table test_login;
drop trigger test_trigger05;
drop trigger test_trigger06;

 

trigger

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原文地址:http://www.cnblogs.com/heibaitan/p/4206759.html

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