Oracle触发另一个表的更新

Question

我正在尝试在Oracle中创建触发器。 我知道sql，但我从未创建过触发器。 我有以下代码：

create or replace trigger "PASSENGER_BOOKING_T1"
AFTER
insert on "PASSENGER_BOOKING"
for each row
begin
IF (:NEW.CLASS_TYPE == 'ECO')

SELECT F.AVL_SEATS_ECOCLASS,F.FLIGHT_ID INTO SEAT, FLIGHT_INFO 
FROM BOOKING B, JOURNEY_FLIGHT J, FLIGHT F 
WHERE B.JOURNEY_ID = J.JOURNEY_ID and F.FLIGHT_ID = J.FLIGHT_ID;

UPDATE FLIGHT 
SET AVL_SEATS_ECOCLASS = (SEAT-1)
WHERE FLIGHT_ID = FLIGHT_INFO;

END IF;
end;​

当Passenger_Booking表中有插入内容时，将触发此触发器。 座位数减少了一个（在不同的桌子上）。

选择查询应该没问题，但是某处有问题。 有人可以建议什么吗？

我将身体部位改为这个，但是仍然有问题：

UPDATE FLIGHT 
SET AVL_SEATS_ECOCLASS =
  (SELECT F.AVL_SEATS_ECOCLASS FROM BOOKING B, JOURNEY_FLIGHT J, FLIGHT F WHERE B.JOURNEY_ID = J.JOURNEY_ID and F.FLIGHT_ID = J.FLIGHT_ID;
);

Answer 1

1. IF语句需要THEN
2. 在PL / SQL中，使用=来测试是否相等，而不是==
3. 您需要声明要选择的变量

当我做这三件事时，我会得到这样的东西

create or replace trigger PASSENGER_BOOKING_T1
  AFTER insert on PASSENGER_BOOKING
  for each row
declare
  l_seat       flight.seat%type;
  l_flight_id  flight.flight_id%type;
begin
  IF (:NEW.CLASS_TYPE = 'ECO')
  THEN
    SELECT F.AVL_SEATS_ECOCLASS,F.FLIGHT_ID 
      INTO l_seat, l_flight_id
      FROM BOOKING B, 
           JOURNEY_FLIGHT J, 
           FLIGHT F 
     WHERE B.JOURNEY_ID = J.JOURNEY_ID 
       and F.FLIGHT_ID = J.FLIGHT_ID;

    UPDATE FLIGHT 
       SET AVL_SEATS_ECOCLASS = (l_seat-1)
     WHERE FLIGHT_ID = l_flight_id;   
  END IF;
end;​

除了这些语法错误，如果SELECT INTO语句正确，我会感到震惊。 SELECT INTO必须恰好返回1行。 您的查询几乎肯定会返回多行，因为没有谓词会将查询限制为特定的航班或特定的预订。 大概您想加入PASSENGER_BOOKING表中的一列或多列。

此外，如果这不是家庭作业，则请确保您了解这种触发器在多用户环境中无法正常工作。

Answer 2

只是一个疯狂的猜测

编辑贾斯汀指出（感谢贾斯汀）平等检查

create or replace trigger "PASSENGER_BOOKING_T1"
AFTER
insert on "PASSENGER_BOOKING"
for each row
declare
   v_flight_id  FLIGHT.FLIGHT_ID%TYPE;
begin
IF (:NEW.CLASS_TYPE = 'ECO') THEN

SELECT F.ID into v_flight_id
FROM BOOKING B, JOURNEY_FLIGHT J, FLIGHT F 
WHERE B.ID = :NEW.BOOKING_ID -- note that I've made this up
AND B.JOURNEY_ID = J.JOURNEY_ID AND F.FLIGHT_ID = J.FLIGHT_ID;

UPDATE FLIGHT 
SET AVL_SEATS_ECOCLASS = (SEAT-1)
WHERE ID = v_flight_id;

END IF;
end;​