MySQL查詢問題：像系統預訂

Question

有可能或不可以保留的房間。預訂日期從（日期）至（日期）。人按日期搜索房間：from_field和till_field。試圖找到一個房間是否可用。

SELECT rooms.* FROM rooms 
LEFT JOIN reservations ON reservations.room_id = rooms.id 
WHERE (reservations.from > till_field OR reservations.till < from_field) 

問題：如果單個保留成功，那麼即使另一個保留佔用了該位置，似乎該查詢仍有可用空間。

Answer 1

如何檢索配有沒有resevations可言：

如果沒有預訂，將有查詢返回的沒有reservations排=>您必須檢查也（reservations.room_id IS NULL ）：

SELECT rooms.* FROM rooms 
LEFT JOIN reservations ON reservations.room_id = rooms.id 
WHERE reservations.room_id IS NULL -- if there is no reservations 
     OR reservations.from > till_field 
     OR reservations.till < from_field 

但真正得到想要的東西歐，你必須檢查的房間沒有任何保留有：

• fromDate or tillDate between from_field and till_field

OR

• fromDate < from_field and tillDate > till_field

SELECT rooms.* 
    FROM rooms 
WHERE NOT EXISTS (SELECT NULL 
        FROM reservations 
        WHERE reservations.room_id = rooms.id 
        AND ((
          reservations.from BETWEEN from_field AND till_field 
          OR 
          reservations.till BETWEEN from_field AND till_field 
         ) 
         OR 
         (
          reservations.from < from_field 
          AND reservations.till > till_field 
         ) 
         ) 
       )