对另一个查询的结果执行查询？

Question

我有一个疑问：

SELECT availables.bookdate AS Date, DATEDIFF(now(),availables.updated_at) as Age
FROM availables
INNER JOIN rooms
ON availables.room_id=rooms.id
WHERE availables.bookdate BETWEEN '2009-06-25' AND date_add('2009-06-25', INTERVAL 4 DAY) AND rooms.hostel_id = 5094
GROUP BY availables.bookdate

返回类似：

Date               Age
2009-06-25         0
2009-06-26         2
2009-06-27         1
2009-06-28         0
2009-06-29         0

然后我怎样才能对返回的行数进行计数..（在本例中为 5）以及年龄的总和？ 仅返回一行包含计数和总和？

Count         SUM
5             3

谢谢

Answer 1

通常您可以将查询的结果（基本上是一个表）插入作为 FROM 子句源 另一个查询，所以会写成这样：

SELECT COUNT(*), SUM(SUBQUERY.AGE) from
(
  SELECT availables.bookdate AS Date, DATEDIFF(now(),availables.updated_at) as Age
  FROM availables
  INNER JOIN rooms
  ON availables.room_id=rooms.id
  WHERE availables.bookdate BETWEEN '2009-06-25' AND date_add('2009-06-25', INTERVAL 4 DAY) AND rooms.hostel_id = 5094
  GROUP BY availables.bookdate
) AS SUBQUERY

Answer 2

您只需将查询包装在另一个查询中即可：

SELECT COUNT(*), SUM(Age)
FROM (
    SELECT availables.bookdate AS Count, DATEDIFF(now(),availables.updated_at) as Age
    FROM availables
    INNER JOIN rooms
    ON availables.room_id=rooms.id
    WHERE availables.bookdate BETWEEN '2009-06-25' AND date_add('2009-06-25', INTERVAL 4 DAY) AND rooms.hostel_id = 5094
    GROUP BY availables.bookdate
) AS tmp;

Answer 3

我不知道你是否需要包装它。 这行不通？

SELECT COUNT(*), SUM(DATEDIFF(now(),availables.updated_at))
FROM availables
INNER JOIN rooms    ON availables.room_id=rooms.id
WHERE availables.bookdate BETWEEN '2009-06-25' 
  AND date_add('2009-06-25', INTERVAL 4 DAY)
  AND rooms.hostel_id = 5094
GROUP BY availables.bookdate);

如果您的目标是返回两个结果集，那么您需要将其临时存储在某个地方。

Answer 4

请注意，您的初始查询可能不会返回您想要的内容：

SELECT availables.bookdate AS Date, DATEDIFF(now(),availables.updated_at) as Age 
FROM availables INNER JOIN rooms ON availables.room_id=rooms.id 
WHERE availables.bookdate BETWEEN  '2009-06-25' AND date_add('2009-06-25', INTERVAL 4 DAY) AND rooms.hostel_id = 5094 GROUP BY availables.bookdate

您正在按图书日期进行分组，但您没有在查询的第二列上使用任何分组功能。

您可能正在寻找的查询是：

SELECT availables.bookdate AS Date, count(*) as subtotal, sum(DATEDIFF(now(),availables.updated_at) as Age)
FROM availables INNER JOIN rooms ON availables.room_id=rooms.id
WHERE availables.bookdate BETWEEN '2009-06-25' AND date_add('2009-06-25', INTERVAL 4 DAY) AND rooms.hostel_id = 5094
GROUP BY availables.bookdate

Answer 5

选择 c.类别名称， SUM(p.UnitsInStock) AS TotalStock 从 产品展示 加入 类别 c 在 p.CategoryID = c.CategoryID 分组依据 c.类别名称；