来自两个表 ORACLE 的总和值

Question

我希望将两个不同表中的两个值用作第三个表中的总计。

例如：

1. 表accommodation和flight
2. acc_price用价值从增加价值flight_price
3. 将这些值相加以用于表预订 subtotal

我尝试过的事情；

SELECT  F.FLI_PRICE + AC.ACC_PRICEPN
INTO    R.SUBTOTAL
FROM    HOLIDAY_RESERVATION R, FLIGHT F, ACCOMMODATION AC;

更新

我希望将 Leigh 的代码添加到触发器中，我尝试了以下操作，但出现了突变错误

CREATE OR REPLACE TRIGGER HR_SUBTOTAL
AFTER DELETE OR INSERT OR UPDATE ON HOLIDAY_RESERVATION
FOR EACH ROW
BEGIN
UPDATE HOLIDAY_RESERVATION R SET SUBTOTAL = 
   NVL((SELECT F.FLI_PRICE FROM FLIGHT F WHERE F.FLI_ID = R.IN_FLIGHT_ID), 0) +
   NVL((SELECT F.FLI_PRICE FROM FLIGHT F WHERE F.FLI_ID = R.OUT_FLIGHT_ID), 0) +
   NVL((SELECT AC.ACC_PRICEPN FROM ACCOMMODATION AC WHERE AC.ACC_ID = R.ACC_ID), 0);
END;
/

ERROR at line 1:
ORA-04091: table LATIN.HOLIDAY_RESERVATION is mutating, trigger/f
ORA-06512: at "LATIN.HR_SUBTOTAL", line 2
ORA-04088: error during execution of trigger 'LATIN.HR_SUBTOTAL'

Answer 1

要使用其他表中可能具有空值的值的总和来更新列，请执行以下操作：

UPDATE Holiday_Reservation R SET Subtotal = 
   NVL((SELECT F.Fli_Price FROM Flight F WHERE F.Fli_ID = R.In_Flight_ID), 0) +
   NVL((SELECT F.Fli_Price FROM Flight F WHERE F.Fli_ID = R.Out_Flight_ID), 0) +
   NVL((SELECT AC.Acc_PricePn FROM Accommodation AC WHERE AC.Acc_ID = R.Acc_ID), 0);

在触发器中，这看起来像这样：

CREATE OR REPLACE TRIGGER HR_SUBTOTAL
BEFORE INSERT OR UPDATE ON HOLIDAY_RESERVATION
FOR EACH ROW
BEGIN
   SELECT 
      NVL((SELECT F.Fli_Price FROM Flight F WHERE F.Fli_ID = :new.In_Flight_ID), 0) +
      NVL((SELECT F.Fli_Price FROM Flight F WHERE F.Fli_ID = :new.Out_Flight_ID), 0) +
      NVL((SELECT AC.Acc_PricePn FROM Accomodation AC WHERE AC.Acc_ID = :new.Acc_ID), 0)
      INTO :new.Subtotal
   FROM dual;
END;
/