使用MySQL计算每个时间间隔内的记录数

我有一个MySQL查询，我正在运行该查询，以计算在15分钟的时间间隔内，在任何给定的小时（在任何给定的一天等）内，一个用户已经预订了多少个电话。到目前为止，我已经：

    SELECT
date_action,
DATE_FORMAT(date_action, "%i") AS minute,
CASE 
    WHEN minute(date_action) BETWEEN 0 and 14 THEN '00'
    WHEN minute(date_action) BETWEEN 15 and 29 THEN '15'
    WHEN minute(date_action) BETWEEN 30 and 44 THEN '30'
    WHEN minute(date_action) BETWEEN 45 and 59 THEN '45'
END AS intervals
FROM
clients
WHERE
HOUR(date_action) = 09
AND DAY(date_action) = 15
AND MONTH(date_action) = 07
AND YEAR(date_action) = 2013

这一点很好，但我缺少的神奇成分是分配给每个间隔的调用数的“计数”，例如，上面的代码生成：

Date_time - Minute - Interval
2013-07-15 09:54:24 - 54 - 45
2013-07-15 09:29:32 - 29 - 15
2013-07-15 09:13:33 - 13 - 00
2013-07-15 09:53:53 - 53 - 45
2013-07-15 09:00:49 - 00 - 00

因此，我将分钟数转换为时间间隔，因为我只想为每个时间间隔返回一行，然后在其中附加一列，其中包含该时间间隔内的呼叫数，即

Interval - Count
45 - 2
15 - 1
00 - 2

---

我觉得我在这件事上撞砖墙的时间太长了，所以任何帮助都将不胜感激。虽然查询后会进行一些后处理，但如果可能的话，我更愿意使用SQL完成这一切。：）

您可以按间隔分组并选择计数

SELECT
    count(date_action) as count,
    CASE 
        WHEN minute(date_action) BETWEEN 0 and 14 THEN '00'
        WHEN minute(date_action) BETWEEN 15 and 29 THEN '15'
        WHEN minute(date_action) BETWEEN 30 and 44 THEN '30'
        WHEN minute(date_action) BETWEEN 45 and 59 THEN '45'
    END AS intervals
FROM
    clients
WHERE
    HOUR(date_action) = 09
    AND DAY(date_action) = 15
    AND MONTH(date_action) = 07
    AND YEAR(date_action) = 2013
    AND rep_id = 28
GROUP BY intervals

那将是另一种方式

---

%是模运算符

OMG，我怎么没看到。我猜又坐得离我的屏幕太近了！非常感谢。：）

select period, Sum(NumberOfTimes) as NumberOfTimes
From
(Select minute(date_action) % 15 as period, 1 as NumberOfTimes
From Clients
WHERE
    HOUR(date_action) = 09
    AND DAY(date_action) = 15
    AND MONTH(date_action) = 07
    AND YEAR(date_action) = 2013
    AND rep_id = 28
) dummyName
Group By period