SQL是否正确查询

Question

鉴于这些关系，您如何查询以下内容： 预订至少退休金的游客（姓名和电子邮件）评分大于9 ，但没有预订任何三星级酒店 评级小于9 。

以下是否正确？

SELECT Tourists.name, Tourists.email
FROM Tourists
WHERE EXISTS (
    SELECT id FROM Bookings
    INNER JOIN Tourists ON Bookings.touristId=Tourists.id 
    INNER JOIN AccomodationEstablishments ON Bookings.accEstId=AccomodationEstablishments.id
    INNER JOIN AccomodationTypes ON AccomodationEstablishments.accType=AccomodationTypes.id 
    WHERE   AccomodationTypes.name = 'Pension' AND 
        AccomodationEstablishments.rating > 9
) AND NOT EXISTS (
    SELECT id FROM Bookings
    INNER JOIN Tourists ON Bookings.touristId=Tourists.id 
    INNER JOIN AccomodationEstablishments ON Bookings.accEstId=AccomodationEstablishments.id
    INNER JOIN AccomodationTypes ON AccomodationEstablishments.accType=AccomodationTypes.id 
    WHERE   AccomodationTypes.name = 'Hotel' AND 
        AccomodationEstablishments.noOfStars = 3 AND 
        AccomodationEstablishments.rating < 9
)

Answer 1

我会使用聚合和having：

来做到这一点

SELECT t.name, t.email
FROM Bookings b INNER JOIN
     Tourists t
     ON b.touristId = t.id INNER JOIN
     AccomodationEstablishments ae
     ON b.accEstId = ae.id INNER JOIN
     AccomodationTypes a
     ON ae.accType = a.id 
GROUP BY t.name, t.email
HAVING SUM(CASE WHEN a.name = 'Pension' AND ae.rating > 9 THEN 1 ELSE 0 END) > 0 AND
       SUM(a.name = 'Hotel' AND ae.noOfStars = 3 AND ae.rating < 9 THEN 1 ELSE 0 END)= 0;

您的方法也有效，但在子查询中可能需要t.id。