一.觸發器是什么
觸發器是數據庫中,隱含被執行的存儲過程存儲過程,當發生特定的事件時,orcle會自動執行觸發器相對應的代碼.
二.觸發器的分類
1.DML觸發器
2.DDL觸發器
3.INSTEAD 觸發器
4.事件觸發器
三.例子
CREATE OR REPLACE TRIGGER upd_esp_category
BEFORE INSERT OR UPDATE
OF email
ON ex_edm_task_detail
FOR EACH ROW
DECLARE
v_category VARCHAR2(64);
BEGIN
SELECT esp_name INTO v_category
FROM ex_edm_esp
WHERE mail_suffix=SUBSTR(:new.email,INSTR(:new.email,'@',1,1)+1, LENGTH(:new.email));
:new.category := v_category;
EXCEPTION
WHEN no_data_found THEN
:new.category := '未知';
WHEN too_many_rows THEN
:new.category := '未知';
WHEN OTHERS THEN
:new.category := '未知';
END;再來一個例子:
create or replace trigger wf_tri_user_list before insert or update or delete on user_list
for each row
declare
uid varchar2(10); useq varchar2(10); asql varchar2(200); namea varchar2(200); nameb varchar2(200);
begin
namea:=NULL;
nameb:=NULL;
if inserting then
insert into wflow.bpm_org_user(userid,username,diaplayname,seq) values(:NEW.user_id,:NEW.user_name,:NEW.user_realname,:NEW.user_id);
dbms_output.put_line('insert trigger is chufale 
..');
end if;
if updating then
if (:NEW.user_name<>:OLD.user_name) and (:NEW.user_realname<>:OLD.user_realname) then
namea:=:NEW.user_name;
nameb:=:NEW.user_realname;
asql:='update wflow.bpm_org_user set diaplayname=:1 where username=:2';
execute immediate asql using namea,nameb;
else
if :NEW.user_name<>:OLD.user_name then
namea:=:NEW.user_name;
asql:='update wflow.bpm_org_user set user_name=:1 where username=:2';
execute immediate asql using namea;
else
if :NEW.user_realname<>:OLD.user_realname then
nameb:=:NEW.user_realname;
asql:='update wflow.bpm_org_user set diaplayname=:1 where username=:2';
execute immediate asql using nameb,:OLD.user_id;
end if;
end if;
end if;
end if;
if deleting then
update wflow.bpm_org_jobusers set userid = 0 where :OLD.user_id =userid and parentid=-1;
delete from wflow.bpm_org_jobusers where userid = :OLD.user_id;
delete wflow.bpm_org_user where userid=:OLD.user_id;
end if;
commit;
end;
:NEW 和:OLD使用方法和意義，new 只出現在insert和update時，old只出現在update和delete時。在insert時new表示新插入的行數據，update時new 表示要替換的新數據、old表示要被更改的原來的數據行，delete時old表示要被刪除的數據。
注意：
在觸發器中不能使用commit。