Oracle SQL 中触发器的 If Else 条件答案

【问题标题】：If Else Condition at Trigger in Oracle SQLOracle SQL 中触发器的 If Else 条件
【发布时间】：2012-12-11 11:32:12
【问题描述】：

我有两张桌子。它们是

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”。当在支付设备中插入新行时，我想更新卡表中的信用。费用取决于用户类型。但是如果用餐类型是客人，每个人都必须支付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;

但我收到此错误： PL/SQL: ORA-00971: missing SET keyword, PL/SQL: SQL Statement ignored。你能帮帮我吗？

【问题讨论】：

标签： sql database oracle triggers

【解决方案1】：

好吧，经过一番研究，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;

感谢您的帮助和建议。

【讨论】：

【解决方案2】：

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;

【讨论】：

它仍然给出错误 ORA-04091：表 SYSTEM.PAYMENTDEVICE 正在变异，触发器/函数可能看不到它 ORA-06512：在“SYSTEM.TRG_PAYMONEY1”，第 2 行 ORA-04088：错误期间触发器“SYSTEM.TRG_PAYMONEY1”的执行

【解决方案3】：

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'update' 语句的工作原理的更多信息，请参阅此文档，

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;

类似的，

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

【讨论】：

【解决方案4】：

您的更新声明应该是（WHERE 应该在 SET 之后）

UPDATE CARD
SET CREDIT = 
(CASE MEALTYPE

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

【讨论】：