ORACLE的触发器TRIGGER的用法
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;