ORACLE的TRIGGER的用法

ORACLE的TRIGGER的用法　 http://www.8888r.com/blog/user/oracle/archives/2006/11045.html     看过这个篇文章之后,对自己的提高很大,我写过很多存储过程,很多函数,很多程序包,唯独没有写过TRIGGER,其实自己对TRIGGER的理解还不是很深,一直想试试,可惜没有机会.看过此文章后,觉得自己应该有能力写一个非常标准的TRIGGER了.

    附原文:

    原文引自 日月明王

                           TRIGGER之我见

                                                   日月明王

                               http://spaces.msn.com/sunmoonking/

  1. trigger 是自动提交的，不用COMMIT，ROLLBACK

  2. trigger最大为32K，如果有复杂的应用可以通过在TRIGGER里调用PROCEDURE或FUNCTION来实现。

  3. 语法CREATE OR REPLACE TRIGGER <trigger_name>

<BEFORE | AFTER> <ACTION>

ON <table_name>

DECLARE

 <variable definitions>

BEGIN

  <trigger_code>

EXCEPTION

  <exception clauses>

END <trigger_name>;

/

  4. 相关命令

    create trigger

    create any trigger

    administer database trigger

    alter any trigger

    drop any trigger

  5. 对列做触发（of）（行的触发是最常见的，不在这里列出

             1  create or replace trigger tri_wwm

             2  before update of id on wwm2 for each row

             3  declare the_str VARCHAR2(40):='update on wwm2''s id column';

             4  begin

             5      dbms_output.put_line(the_str);

             6* end tri_wwm;

           SQL> /

           Trigger created.

           SQL> update wwm2 set id=3;

           update on wwm2's id column

           1 row updated.

      6. Referencing 别名

          测试数据

           SQL> select * from wwm2;

                   ID NAME

           ---------- ----------

                    1 wwm

                    2 china

          建测试用日志表

             1  create table wwm_log

             2  (o_id number(8),o_name varchar2(10),

             3  n_id number(8),n_name varchar2(10),

             4* op_by varchar2(20),op_date date)

           SQL> /

           Table created.

           建立 触发器

             create or replace trigger tri_refer

            after update of id on wwm2 referencing new as new old as old for each row

            begin

                insert into wwm_log values (:old.id,:old.name,:new.id,:new.name,sysdate,user);

            end;

            /

            更新表以触发事件

           SQL> update wwm2 set id=8 where id=2;

           update on wwm2's id column

           1 row updated.

           SQL> select * from wwm_log;

                 O_ID O_NAME           N_ID N_NAME     OP_DATE   OP_USER

           ---------- ---------- ---------- ---------- --------- -----------------

                    2 china               8 china      09-MAR-06 SYSTEM

                 大家可以用这个方法来对一些操作做日志

      7.Disable/Enable

         ALTER  TRIGGER  tri_refer DISABLE/ENABLE

         ALTER  TABLE wwm2 DISABLE/ENABLE ALL TRIGGERS;

         ALTER TRIGGER tri_refer RENAME TO tri_reference;

      TRIGGER的种类还有很多，如DDL和SYSTEM的触发器，下次用到时再写吧。