從第一MySQL查詢

Question

另一個表匹配結果添加列這是我在choosen期間可用客房查詢：

SELECT rooms.room_id 
    FROM rooms 
WHERE rooms.room_id NOT IN ( 
    SELECT reservations.room_id 
    FROM reservations 
    WHERE ( reservations.arrivaldate >= $arrival_datetime 
      AND reservations.departuredate <= $departure_datetime 
     ) 
     OR ( reservations.arrivaldate <= $arrival_datetime 
      AND reservations.departuredate >= $arrival_datetime 
     ) 
     OR ( reservations.arrivaldate <= $departure_datetime 
      AND reservations.departuredate >= $departure_datetime 
     ) 
); 

如何爲選定時段（arrival_datetime departure_datetime從$至$）加平均房價柱從另一個表（room_prices_table）中，查詢從上面返回的每個room_id。所以，我需要在列看看衛生組織的名字是一樣的... ROOM_ID

room_prices_table: 
date 
room0001 
room0002 
room0003 
... 

喜歡的東西

SELECT AVG(room0003) 
    FROM room_prices_table 
WHERE datum IS BETWEEN $arrival_datetime 
        AND $departure_datetime 

？

Answer 1

事情是這樣的：

SELECT 
    r.room_id, 
    COALESCE(AVG(rpt.room0003), 0) AS AVERAGE_RATE 
FROM rooms r 
    LEFT OUTER JOIN room_prices_table rpt 
    ON r.room_id = rpt.room_id 
AND 
    rpt.datum BETWEEN $arrival_datetime AND $departure_datetime 
WHERE 
    r.room_id NOT IN (
    SELECT reservations.room_id 
     FROM reservations 
     WHERE (reservations.arrivaldate >= $arrival_datetime AND 
      reservations.departuredate <= $departure_datetime) OR 
      (reservations.arrivaldate <= $arrival_datetime AND 
      reservations.departuredate >= $arrival_datetime) OR 
      (reservations.arrivaldate <= $departure_datetime AND 
      reservations.departuredate >= $departure_datetime) 
    ) 
GROUP BY 
    r.room_id; 

使用COALESCE function確保我們的客房，在room_prices_table沒有信息得到0，而不是空的。