我正在尝试编写一个触发器,该触发器在插入的情况下会执行以下操作:
1)计算飞机上的座位数
2)计算已经在此航班上的乘客人数
3)比较这些值,然后在表中插入新行,或者引发错误,指出飞机上没有更多的自由座位了。
这是我的代码:
DELIMITER //
USE AIRPORT;
CREATE TRIGGER CHECK_FOR_PLACES
BEFORE INSERT ON TICKET
FOR EACH ROW
BEGIN
DECLARE NUM_OF_PLACES INT;
DECLARE NUM_OF_PASSENGERS INT;
SET NUM_OF_PLACES := (SELECT CAPACITY
FROM AIRPLANE
INNER JOIN FLIGHT ON FLIGHT.ID_AIRPLANE = AIRPLANE.ID_AIRPLANE
WHERE FLIGHT.ID_FLIGHT = NEW.ID_FLIGHT);
SET NUM_OF_PASSENGERS := (SELECT COUNT(*)
FROM TICKET
WHERE TICKET.ID_FLIGHT = NEW.ID_FLIGHT);
IF NUM_OF_PASSENGERS >= NUM_OF_PLACES THEN
SIGNAL SQLSTATE '-20000' SET MESSAGE_TEXT = 'NO MORE PLACES ON THIS FLIGHT';
END IF;
END//
DELIMITER ;
尝试编译脚本后,出现以下错误:
Error Code: 2014. Commands out of sync; you can't run this command now
我不知道此错误的原因可能是什么。我将不胜感激。预先感谢
答案 0 :(得分:0)
use airport
是一个单独的语句,由于您更改了定界符,因此应以//终止:
DELIMITER //
USE AIRPORT//
...