Question

我正在尝试在Oracle中创建触发器。我知道sql但我以前从未创建过触发器。我有这段代码：

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表中有插入时，将触发此触发器。座位容量减少一个（在不同的桌子上）。

选择查询应该没问题，但某处有问题。有人可以提出什么建议吗？

我将身体部位更改为此但仍有问题：

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

IF语句需要THEN
在PL / SQL中，您使用=来测试相等性，而不是==
您需要声明要选择的变量

当我做这三件事时，我会得到类似的东西

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;

除了那些语法错误之外，如果SELECT INTO语句是正确的，我会感到震惊。 SELECT INTO必须返回1行。您的查询几乎肯定会返回多行，因为没有谓词会限制查询到特定航班或特定预订。据推测，您希望加入PASSENGER_BOOKING表中的一个或多个列。

此外，如果这不是作业分配，请确保您了解此类触发器在多用户环境中无法正常工作。

Answer 2

只是一个狂野的猜测

Justin指出（感谢Justin）平等检查

编辑

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;

Oracle在另一个表中触发更新

2 个答案: