Question

我在SQL Server中建立了一个酒店预订数据库。其中三个表格如下：

这些表中的相关列是：

Booking：BookingID（PK），CheckInDate，CheckoutDate
RoomBooking：RoomBookingID（PK），FK_Booking_ID（FK），FK_RoomID（FK）
Room：RoomID（PK）

现在我写了一个SQL查询（如下所示），试图找出某个日期（2017-10-02至2017-10-04）的免费房间。代码解决了问题，但变得非常复杂。我知道如何通过表CheckInDate中的CheckOutDate和RoomBooking来解决这个问题，但我希望这个设置能够正常运行。您对如何使下面的代码变得简单有任何想法吗？

BR / Mike

SELECT FK_RoomID 
FROM RoomBooking
WHERE FK_RoomID IN 
      (SELECT FK_RoomID 
       FROM RoomBooking
       WHERE FK_BookingID NOT IN    
             (SELECT BookingID 
              FROM Booking
              WHERE CheckInDate <= '2017-10-04'
                AND CheckOutDatum > '2017-10-02')   
             )
         AND FK_RoomID NOT IN 
             (SELECT FK_RoomID 
              FROM RoomBooking
              WHERE FK_BookingID IN     
                    (SELECT FK_BookingID 
                     FROM RoomBooking
                     WHERE FK_RoomID IN     
                           (SELECT FK_RoomID  
                            FROM RoomBooking
                            WHERE FK_BookingID IN   
                                  (SELECT FK_BookingID 
                                   FROM RoomBooking
                                   WHERE FK_BookingID NOT IN 
                                         (SELECT BookingID 
                                          FROM Booking
                                          WHERE CheckInDate <= '2017-10-04'
                                            AND CheckOutDate > '2017-10-02')
                                         )
                                   )
                            )
                        AND FK_BookingID NOT IN 
                            (SELECT FK_BookingID 
                             FROM RoomBooking
                             WHERE FK_BookingID NOT IN  
                                   (SELECT BookingID 
                                    FROM Booking
                                    WHERE CheckInDate <= '2017-10-04'
                                      AND CheckOutDate > '2017-10-02')
                                   )
                            );

Answer 1

我希望这样的查询：

select r.*
from room r
where not exists (select 1
                  from roombooking rb join
                       booking b
                       on b.bookingid = r.bookingid
                  where r.roomid = rb.roomid and
                        '2017-10-02' < b.CheckOutDate and
                        '2017-10-04' >= b.CheckInDate
                 );

这假定在有人结账的那天可以办理入住手续。

我不明白为什么你用fk_为某些列添加前缀。外键关系应该从具有相同名称的键（以及显式声明的键）中显而易见。许多数据库都支持ANSI标准USING子句，并且使用不同的密钥名称会阻止您使用它。

SQL太复杂的嵌套查询 - 你能让它变得更简单吗？

1 个答案: