从这些表格中获取最受欢迎的结果

Question

这是我的表定义：

表___房间：

|--------|-----------|--------|----------|
|ROO_Id  |ROO_HotelId|ROO_Name|ROO_Number|
|--------|-----------|--------|----------|
|       1|AAA00      |Room 12 |        12|
|       2|AAA00      |Room 14 |        14|
|       3|AAA00      |Room 16 |        16|
|       4|ZZZ99      |Room 11 |        11|
|       5|ZZZ99      |Room 22 |        22|
|       6|ZZZ99      |Room 33 |        33|
|--------|-----------|--------|----------|

表___预订：

|--------|-----------|----------|
|BOO_Id  |BOO_HotelId|BOO_RoomId|
|--------|-----------|----------|
|       1|AAA00      |         1|
|       2|AAA00      |         1|
|       3|AAA00      |         3|
|       4|ZZZ99      |         5|
|       5|ZZZ99      |         5|
|       6|ZZZ99      |         5|
|--------|-----------|----------|

其实我有：

• AAA00 的预订数量 = 3
  

• AAA00 的房间数 = 3

---

我想仅列出 AAA00 属性的房间，并按预订数量中最受欢迎的房间对其进行排名。

所以我使用这个查询：

SELECT r.ROO_Number BOO_RoomId, 
  ( ( ifnull(cnt_book,0)*100)/(SELECT count(*) FROM ___Bookings)) percentage, 
  ifnull(cnt_book,0) `count` 
FROM ___Rooms r 
   LEFT JOIN (
               SELECT BOO_RoomId, count(*) cnt_book 
               FROM ___Bookings 
               WHERE BOO_HotelId='AAA00' 
               GROUP BY BOO_RoomId
             ) cnt ON r.ROO_Id=cnt.BOO_RoomId 
ORDER BY percentage DESC

这个查询的预期结果是：

• 1 - 房间 2 - 2 次预订 - 66.66%

• 2 - 房间 3 - 1 次预订 - 33.33%

• 3 - 房间 2 - 0 预订 - 00.00$

但它会将所有房间都归还给我。

你能帮我解决这个问题吗？

谢谢。

Answer 1

解决方案

使用CASE 和SUM 将每个房间的所有预订加在一起。然后，JOIN 进行子查询，使酒店总预订量可用于每一行。

SELECT r.ROO_Name
     , Sum(CASE WHEN BOO_id IS NULL THEN 0 ELSE 1 END) NumBookings
     , Concat(
         Format(
           Sum(CASE WHEN BOO_id IS NULL THEN 0 ELSE 1 END) 
           / TotalBookings 
           * 100
         , 0)
       , '%') AS PercentageTotal
  FROM (  __Rooms r LEFT JOIN __Bookings b ON r.ROO_Id = b.BOO_RoomId
       ) INNER JOIN (SELECT BOO_HotelId
                          , Count(*) AS TotalBookings
                       FROM __Bookings 
                      GROUP BY BOO_HotelId
                    ) AS TotalHotelBookings 
                 ON r.ROO_HotelId = TotalHotelBookings.BOO_HotelId
 WHERE r.ROO_HotelId = 'AAA00'
 GROUP BY r.ROO_Name
 ORDER BY r.ROO_Name
;

结果集

ROO_Name  NumBookings  PercentageTotal
--------  -----------  ---------------
Room 12             2              67%
Room 14             0               0%
Room 16             1              33%

关键点

Sum(CASE WHEN BOO_id IS NULL THEN 0 ELSE 1 END)

Answer 2

差不多应该是这样的：

SELECT
    foo.ROO_Id,
    foo.ROO_Name, 
    foo.cnt, 
    (foo.cnt * 100.0) / (SELECT count(*) FROM ___Bookings WHERE BOO_HotelId = foo.ROO_HotelId) AS percentage
FROM (
    SELECT
        ROO_Id,
        ROO_Name,
        ROO_HotelId,
        (SELECT count(*) FROM ___Bookings b WHERE b.BOO_RoomId = r.ROO_Id) AS cnt
    FROM ___Rooms r
    WHERE ROO_HotelId = 'AAA00'
) AS foo
ORDER BY cnt DESC