MySQL 按小时分组

Question

我正在尝试从我的历史记录表中按小时使用情况获取报告。 历史表是；

CREATE TABLE IF NOT EXISTS `history` (
`history_id` int(11) unsigned NOT NULL AUTO_INCREMENT,
`user_id` int(11) unsigned NOT NULL DEFAULT '0',
`created` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
PRIMARY KEY (`history_id`),
KEY `user_id` (`user_id`),
KEY `created` (`created`)
) ENGINE=InnoDB  DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci AUTO_INCREMENT=1 ;

我想按 HOUR 和 COUNT 对给定日期范围内的所有记录进行分组。

Hours            |    Usage
------------------------------------
00:00-01:00      |      5
01:00-02:00      |      9
02:00-03:00      |      0 (or NULL)
03:00-04:00      |      20
...
...
...
22:00-23:00      |      11
23:00-00:00      |      1

我使用了类似这样的查询，但它没有显示所有时间。

SELECT 

CASE 
  WHEN HOUR(created) BETWEEN 0 AND 1 THEN '00:00 - 01:00'
  WHEN HOUR(created) BETWEEN 1 AND 2 THEN '01:00 - 02:00'
  WHEN HOUR(created) BETWEEN 2 AND 3 THEN '02:00 - 03:00'
  WHEN HOUR(created) BETWEEN 3 AND 4 THEN '03:00 - 04:00'
  WHEN HOUR(created) BETWEEN 4 AND 5 THEN '04:00 - 05:00'
  WHEN HOUR(created) BETWEEN 5 AND 6 THEN '05:00 - 06:00'
  WHEN HOUR(created) BETWEEN 6 AND 7 THEN '06:00 - 07:00'
  WHEN HOUR(created) BETWEEN 7 AND 8 THEN '07:00 - 08:00'
  WHEN HOUR(created) BETWEEN 8 AND 9 THEN '08:00 - 09:00'
  WHEN HOUR(created) BETWEEN 9 AND 10 THEN '09:00 - 10:00'
  WHEN HOUR(created) BETWEEN 10 AND 11 THEN '10:00 - 11:00'
  WHEN HOUR(created) BETWEEN 11 AND 12 THEN '11:00 - 12:00'
  WHEN HOUR(created) BETWEEN 12 AND 13 THEN '12:00 - 13:00'
  WHEN HOUR(created) BETWEEN 13 AND 14 THEN '13:00 - 14:00'
  WHEN HOUR(created) BETWEEN 14 AND 15 THEN '14:00 - 15:00'
  WHEN HOUR(created) BETWEEN 15 AND 16 THEN '15:00 - 16:00'
  WHEN HOUR(created) BETWEEN 16 AND 17 THEN '16:00 - 17:00'
  WHEN HOUR(created) BETWEEN 17 AND 18 THEN '17:00 - 18:00'
  WHEN HOUR(created) BETWEEN 18 AND 19 THEN '18:00 - 19:00'
  WHEN HOUR(created) BETWEEN 19 AND 20 THEN '19:00 - 20:00'
  WHEN HOUR(created) BETWEEN 20 AND 21 THEN '20:00 - 21:00'
  WHEN HOUR(created) BETWEEN 21 AND 22 THEN '21:00 - 23:00'
  WHEN HOUR(created) BETWEEN 22 AND 23 THEN '22:00 - 23:00'
  WHEN HOUR(created) BETWEEN 23 AND 24 THEN '23:00 - 00:00'
END AS `Hours`,

COUNT(*) AS `usage`
FROM history
WHERE (created BETWEEN '2012-02-07' AND NOW())
GROUP BY 
  CASE 
    WHEN HOUR(created) BETWEEN 0 AND 1 THEN 1
    WHEN HOUR(created) BETWEEN 1 AND 2 THEN 2
    WHEN HOUR(created) BETWEEN 2 AND 3 THEN 3
    WHEN HOUR(created) BETWEEN 3 AND 4 THEN 4
    WHEN HOUR(created) BETWEEN 4 AND 5 THEN 5
    WHEN HOUR(created) BETWEEN 5 AND 6 THEN 6
    WHEN HOUR(created) BETWEEN 6 AND 7 THEN 7
    WHEN HOUR(created) BETWEEN 7 AND 8 THEN 8
    WHEN HOUR(created) BETWEEN 8 AND 9 THEN 9
    WHEN HOUR(created) BETWEEN 9 AND 10 THEN 10
    WHEN HOUR(created) BETWEEN 10 AND 11 THEN 11
    WHEN HOUR(created) BETWEEN 11 AND 12 THEN 12
    WHEN HOUR(created) BETWEEN 12 AND 13 THEN 13
    WHEN HOUR(created) BETWEEN 13 AND 14 THEN 14
    WHEN HOUR(created) BETWEEN 14 AND 15 THEN 15
    WHEN HOUR(created) BETWEEN 15 AND 16 THEN 16
    WHEN HOUR(created) BETWEEN 16 AND 17 THEN 17
    WHEN HOUR(created) BETWEEN 17 AND 18 THEN 18
    WHEN HOUR(created) BETWEEN 18 AND 19 THEN 19
    WHEN HOUR(created) BETWEEN 19 AND 20 THEN 20
    WHEN HOUR(created) BETWEEN 20 AND 21 THEN 21
    WHEN HOUR(created) BETWEEN 21 AND 22 THEN 22
    WHEN HOUR(created) BETWEEN 22 AND 23 THEN 23
    WHEN HOUR(created) BETWEEN 23 AND 24 THEN 24
END

只有当有记录时才会显示。

Hours            |    Usage
------------------------------------
00:00-01:00      |      5
01:00-02:00      |      9
23:00-00:00      |      1

Answer 1

您现有的查询可以简化为:

SELECT   CONCAT(HOUR(created), ':00-', HOUR(created)+1, ':00') AS Hours
  ,      COUNT(*) AS `usage`
FROM     history
WHERE    created BETWEEN '2012-02-07' AND NOW()
GROUP BY HOUR(created)

要显示每个 小时，包括那些没有数据的小时，您需要与一个包含您想要数据的所有小时的表进行外部联接。您可以使用 UNION 在查询中构建这样的表:

SELECT   CONCAT(Hour, ':00-', Hour+1, ':00') AS Hours
  ,      COUNT(created) AS `usage`
FROM     history
  RIGHT JOIN (
                   SELECT  0 AS Hour
         UNION ALL SELECT  1 UNION ALL SELECT  2 UNION ALL SELECT  3
         UNION ALL SELECT  4 UNION ALL SELECT  5 UNION ALL SELECT  6
         UNION ALL SELECT  7 UNION ALL SELECT  8 UNION ALL SELECT  9
         UNION ALL SELECT 10 UNION ALL SELECT 11 UNION ALL SELECT 12
         UNION ALL SELECT 13 UNION ALL SELECT 14 UNION ALL SELECT 15
         UNION ALL SELECT 16 UNION ALL SELECT 17 UNION ALL SELECT 18
         UNION ALL SELECT 19 UNION ALL SELECT 20 UNION ALL SELECT 21
         UNION ALL SELECT 22 UNION ALL SELECT 23
  )      AS AllHours ON HOUR(created) = Hour
WHERE    created BETWEEN '2012-02-07' AND NOW() OR created IS NULL
GROUP BY Hour
ORDER BY Hour

但是，对于不存在数据的组的处理实际上是业务逻辑的问题，最好将其放置在数据访问层而不是数据库本身:实际上，对于您的应用程序来说，无论何时使用零值都应该是微不足道的缺席一个小时。