Count of number of records in each time interval with MySQL

Question

I have a MySQL query which I'm running to work out how many calls have been booked for a user in any given hour (on any given day etc) within 15 minute time intervals. Thus far I have:

    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

This works well as it is but the magic ingredient I'm missing is a 'count' of the number of calls assigned to each interval, so for example the code above produces:

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

So, I have my minutes converted into intervals as I only want to return 1 row for each interval and then have appended to it a column with the count of the number of calls in that interval, i.e.

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

I feel like I've been banging my head against a brick wall on this one for way too long now so any help would be greatly appreciated. Whilst there is some post-processing going on after the query I would much rather do this all in SQL if possible. :)

Answer 1

You can group by the intervals and select the counts.

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

Answer 2

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

would be another way

% is the modulus operator