MySQL的預訂的可用性，重疊的日期範圍

Question

我有預訂的表：

• ID（INT）
• 量（TINYINT）
• DATE_START（時間戳）
• DATE_END（時間戳）

預訂可以重疊，因此可以同時預訂20個預訂。現在我想要做兩個查詢：

1）檢索在給定時間內的最大數量總和。

2）檢索在給定時間內的最小數量總和。

我不知道如何將的數量相加，只將重疊預訂加在一起，而不是非重疊預訂。任何幫助將不勝感激。

編輯：我畫了一幅畫的清晰度：http://i.imgur.com/8GDLV.png

Answer 1

1. 構建所有預訂邊界的列表（即就發生在所期望的時間段的結束日期）：

   SELECT date_start AS boundary 
       FROM bookings 
       WHERE date_start BETWEEN @start AND @end 
   UNION 
       SELECT date_end 
       FROM bookings 
       WHERE date_end BETWEEN @start AND @end 
   

2. 添加到該所期望的時間段之前立即發生的邊界：

   -- [ from part 1 above ] 
   UNION 
       SELECT MAX(boundary) 
       FROM (
       SELECT MAX(date_start) AS boundary 
       FROM bookings 
       WHERE date_start <= @start 
       UNION ALL 
       SELECT MAX(date_end) 
       FROM bookings 
       WHERE date_end <= @end 
   ) t 
   

3. 使外這個結果和之間的連接bookings表，保持所有的界限，但只有包括預訂，如果它有助於人們同步的數後的邊界：

   FROM bookings RIGHT JOIN (
       -- [ from part 2 above ] 
   ) t ON date_start <= boundary AND boundary < date_end 
   

4. 點心的人在每個邊界數量：

   SELECT IFNULL(SUM(quantity),0) AS simultaneous_people 
   -- [ from part 3 above ] 
   GROUP BY boundary 
   

5. 找出最大和最小：

   SELECT MIN(simultaneous_people), 
        MAX(simultaneous_people) 
   FROM (
       -- [ from part 4 above ] 
   ) t 
   

全部放在一起：

SELECT MIN(simultaneous_people), 
     MAX(simultaneous_people) 
FROM (
    SELECT IFNULL(SUM(quantity),0) AS simultaneous_people 
    FROM bookings RIGHT JOIN (
    SELECT date_start AS boundary 
    FROM bookings 
    WHERE date_start BETWEEN @start AND @end 
    UNION 
    SELECT date_end 
    FROM bookings 
    WHERE date_end BETWEEN @start AND @end 
    UNION 
    SELECT MAX(boundary) 
    FROM (
     SELECT MAX(date_start) AS boundary 
     FROM bookings 
     WHERE date_start <= @start 
    UNION ALL 
     SELECT MAX(date_end) 
     FROM bookings 
     WHERE date_end <= @end 
    ) t 
) t ON date_start <= boundary AND boundary < date_end 
    GROUP BY boundary 
) t 

請參閱sqlfiddle。

Answer 2

沒有在問題中給出的數據結構的分組沒有現場。所以假設你正在分組ID。

1）。獲得最大限度的使用MAX

SELECT MAX(TotalQty) FROM 
(
    SELECT SUM(Quantity) AS TotalQty FROM Bookings 
    WHERE date_End<='<To Date>' 
    AND date_Start>='<From Date>' 
    GROUP BY id 
) SumQty 

2）。爲了獲得最大的分MIN

SELECT MIN(TotalQty) FROM 
(
    SELECT SUM(Quantity) AS TotalQty FROM Bookings 
    WHERE date_End<='<To Date>' 
    AND date_Start>='<From Date>' 
    GROUP BY id 
) SumQty 

See this SQLFiddle