如果在Oracle SQL中触发器的Else Condition

Question

我有两张桌子。他们是

CARD(cardid, credit, usertype,charge)

和

PAYMENTDEVICE(paydevid, paydevip,paydevdate, paydevtime, chargedcardid, mealtype). 

膳食类型可以是“客人”或“标准”。 我想在支付设备中插入新行时更新卡表中的信用。 费用取决于使用类型。 但如果用餐类型是客人，每个人都需要支付5美元。 我尝试使用以下代码

CREATE OR REPLACE TRIGGER  "TRG_PAYMONEY" 
AFTER INSERT
ON PAYMENTDEVICE FOR EACH ROW

BEGIN
UPDATE CARD
WHERE CARDID = :NEW.CHARGEDCARDID
SET CREDIT = 
(CASE MEALTYPE

WHEN "STANDARD" THEN CREDIT - CHARGE
WHEN "GUEST" THEN CREDIT - 5
END);
END;

但我得到这个错误： PL/SQL: ORA-00971: missing SET keyword, PL/SQL: SQL Statement ignored 。 请问你能帮帮我吗？

Answer 1

请按照此语法进行更新，

update table_name set field1='value' where field2='value'

（即）

UPDATE CARD
SET CREDIT = 
(CASE MEALTYPE
WHEN "STANDARD" THEN CREDIT - CHARGE
WHEN "GUEST" THEN CREDIT - 5
END)
 WHERE CARDID = :NEW.CHARGEDCARDID;

有关更多信息， 'update'语句的工作原理请参考此文档，

http://docs.oracle.com/cd/B19306_01/appdev.102/b14261/update_statement.htm

对于你的第二个错误试试这个，

UPDATE CARD
SET CREDIT = 
(CASE 
WHEN MEALTYPE="STANDARD" THEN CREDIT - CHARGE
WHEN MEALTYPE="GUEST" THEN CREDIT - 5
END MEALTYPE) 
 WHERE CARDID = :NEW.CHARGEDCARDID;

像这样的东西，

update card c
set c.credit=(select case when p.mealtype='STANDARD' then c.credit-c.charge
                 when p.mealtype='GUEST' then c.credit-5
            end credit from PAYMENTDEVICE p
           where c.cardid=p.chargedcardid)

fiddle_demo

Answer 2

你update语句应该是（ WHERE后应SET ）

UPDATE CARD
SET CREDIT = 
(CASE MEALTYPE

WHEN "STANDARD" THEN CREDIT - CHARGE
WHEN "GUEST" THEN CREDIT - 5
WHERE CARDID = :NEW.CHARGEDCARDID

Answer 3

请运行此代码..

CREATE OR REPLACE TRIGGER TRG_PAYMONEY1
AFTER INSERT ON PAYMENTDEVICE 
FOR EACH ROW
BEGIN
UPDATE CARD c
SET c.credit=(select case when p.mealtype='STANDARD' then c.credit-c.charge
                 when p.mealtype='GUEST' then c.credit-5
            end result from PAYMENTDEVICE p,card c
           where c.cardid=p.chargedcardid)
WHERE CARDID = :NEW.CHARGEDCARDID;
END;

Answer 4

好吧，经过一些研究并感谢Oracle Documentation，我们解决了这个实现的问题：

CREATE OR REPLACE TRIGGER  "TRG_PAYMONEY" 
AFTER INSERT
ON PAYMENTDEVICE FOR EACH ROW

BEGIN
IF :NEW.MEALTYPE='GUEST' THEN
UPDATE CARD
SET CREDIT = CREDIT - 5
WHERE CARDID = :NEW.CHARGEDCARDID;
ELSE
UPDATE CARD
SET CREDIT = CREDIT - CHARGE
WHERE CARDID = :NEW.CHARGEDCARDID;
END IF;
END;

谢谢你的帮助和建议。