触发器

CREATE [OR REPLACE] TRIGGER trigger_name

AFTER | BEFORE | INSTEAD OF

[INSERT] [[OR] UPDATE [OF column_list]]

[[OR] DELETE]

ON table_or_view_name

[REFERENCING {OLD [AS] old / NEW [AS] new}]

[FOR EACH ROW]

[WHEN (condition)]

pl/sql_block;

启用和禁用触发器

ALTER TRIGGER 触发器名 DISABLE/ENABLE;

删除触发器

DROP TRIGGER 触发器名;

显示有关触发器的信息

select trigger_name from dba_triggers/user_triggers;

显示某个表中的触发器的信息

select trigger_name from dba_triggers/user_triggers where table_name = '表名';

例1：当订单明细商品数量、价格改变时，订单中的金额随之改变

create or replace trigger tri_product

after update of D_QUANTITY,D_PRICE on orderdetail

for each row

declare

       updateSum number;

begin    

       --得到订单明细的商品数量改变后的订单总金额，将订单表中的金额进行修改

       updateSum := :new.D_QUANTITY * :new.D_PRICE - :old.D_QUANTITY * :old.D_PRICE;

       dbms_output.put_line(:old.o_id);

       update orderTab set O_MONEY = O_MONEY + updateSum where O_ID = :old.O_ID;

end;

--测试触发器：订单明细商品数量、价格改变时，订单中的金额随之改变

update orderdetail set d_quantity = 3 where d_id=2;