Question

我创建了此功能，可以检查航班的总费用是否已正确计算。它应该乘以座位的价格，例如400乘以客户要求的座位数，例如2.如果客户正确输入总数，例如，它应该成功返回查询。如果他们没有正确输入总数，例如1000然后它应该提出例外'价格已被错误地计算'。

CREATE FUNCTION check_totalcost() RETURNS trigger AS $check_totalcost$
    DECLARE seatprice int;
    DECLARE noofseats int;
    BEGIN
        SELECT priceperseat INTO seatprice
        FROM flight
        WHERE flightid = flightid;

        SELECT numseats INTO noofseats
        FROM flightbooking
        WHERE flightid = flightid;

        IF(seatprice*noofseats != new.totalcost) THEN
        RAISE EXCEPTION 'price has been calculated incorrectly';

        END IF;
        RETURN NEW;
    END;
    $check_totalcost$ LANGUAGE plpgsql;
    /* This is used to run the function above */
    CREATE TRIGGER insert_totalcost
    BEFORE INSERT OR UPDATE ON flightbooking
    FOR EACH ROW EXECUTE PROCEDURE check_totalcost();

当我错误地输入总数时，它会引发我想要的异常，但是当我正确输入总数时，它也会在应该成功返回查询时引发异常。

Answer 1

查询

SELECT priceperseat INTO seatprice
FROM flight
WHERE flightid = flightid;

SELECT numseats INTO noofseats
FROM flightbooking
WHERE flightid = flightid;

没有意义，因为条件总是正确的。我想你想从插入/更新的记录中获取flightid。使用特殊记录NEW：

WHERE flightid = NEW.flightid;

您的函数中还有一个逻辑错误。座位数也应从new记录中获得。

CREATE OR REPLACE FUNCTION check_totalcost() 
RETURNS trigger AS $check_totalcost$
    DECLARE seatprice int;
    BEGIN
        SELECT priceperseat INTO seatprice
        FROM flight
        WHERE flightid = new.flightid;

        IF seatprice * new.numseats != new.totalcost THEN
            RAISE EXCEPTION 'price has been calculated incorrectly';

        END IF;
        RETURN NEW;
    END;
    $check_totalcost$ LANGUAGE plpgsql;

功能错误 - postgresql

1 个答案: