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我以前做的一個(gè)例子，你參考下吧
第八章 觸發(fā)器(Trigger)
--格式：
create or replace trigger 名稱
[after|before][delete|update|insert]
[on 表 | on schema]
[referencing new as 別名 old as 別名]
[for each row]
declare
....
begin
...
exception
....
end;
--創(chuàng)建一個(gè)delete類型行級(jí)觸發(fā)器
--刪除的一行數(shù)據(jù)保存在:old
create or replace trigger emp_delete_row_trigger
after delete
on emp
referencing new as n old as o
for each row
begin
dbms_output.put_line('emp_delete_row_trigger called.');
dbms_output.put_line('刪除員工：' || :o.empno || ' ' || :o.ename);
end;
delete from emp where empno=7499;
delete from emp;
--創(chuàng)建一個(gè)insert類型行級(jí)觸發(fā)器
--插入的一行新數(shù)據(jù)保存在:new
create or replace trigger emp_insert_row_trigger
after insert
on emp
for each row
begin
dbms_output.put_line('emp_insert_row_trigger called.');
dbms_output.put_line('添加員工：' || :new.empno || ' ' || :new.ename);
end;
insert into emp(empno,ename) values(1,'empxxx');
--創(chuàng)建一個(gè)update類型行級(jí)觸發(fā)器
--修改前的數(shù)據(jù)保存在:old
--修改后的數(shù)據(jù)保存在:new
create or replace trigger emp_update_row_trigger
after update
on emp
for each row
begin
dbms_output.put_line('emp_update_row_trigger called.');
dbms_output.put_line('修改前：' || :old.empno || ' ' || :old.ename);
dbms_output.put_line('修改后：' || :new.empno || ' ' || :new.ename);
end;
update emp
set ename='xxxx'
where empno=7499;
--語句級(jí)觸發(fā)器(update,delete,insert)
create or replace trigger delete_stmt_trigger
after delete
on emp
begin
dbms_output.put_line('delete_stmt_trigger called.');
end;
delete from emp;
--判斷觸發(fā)器類型
----------------------------------------------------------
--每進(jìn)行一次交易，就要調(diào)用觸發(fā)器，自動(dòng)扣除或增加賬戶金額
----------------------------------------------------------
create table account
(
customerName varchar2(30) primary key,
cardID varchar2(8),
currentMoney number
);
insert into account values('Daivd','10010001',5000);
insert into account values('Jason','10010002',3000);
create table trans
(
transDate date,
cardID varchar2(8),
transType varchar2(10),
transMoney number
);
insert into trans
values(sysdate,'10010001','取款',1000);
create or replace trigger trans_trigger
before insert
on trans
for each row
declare
v_currentMoney account.currentMoney%type;
begin
--判斷類型
if :new.transType='取款' then
--取款
select currentMoney into v_currentMoney
from account
where cardID=:new.cardID;

if v_currentMoney < :new.transMoney then
raise_application_error(-20001,'余額不足');
end if;

update account
set currentMoney=currentMoney-:new.transMoney
where cardID=:new.cardID;
else
--存款
update account
set currentMoney=currentMoney+:new.transMoney
where cardID=:new.cardID;
end if;
exception
when no_data_found then
raise_application_error(-20002,'無效的帳戶');
end;
--模式(schema)級(jí)觸發(fā)器
create or replace trigger schema_trigger
before drop
on schema
begin
dbms_output.put_line('schema_trigger called');
dbms_output.put_line(ora_dict_obj_name);
dbms_output.put_line(ora_dict_obj_type);

if ora_dict_obj_name='ACCOUNT' then
raise_application_error(-20003,'ACCOUNT表不能被刪除');
end if;
end;
drop table account;
--ora_dict_obj_name 操作對(duì)象名稱
--ora_dict_obj_type 操作對(duì)象類型
--啟用觸發(fā)器
alter trigger schema_trigger enable;
--禁用觸發(fā)器
alter trigger schema_trigger disable;