Counted value grouped by date range - mysql

Question

From a Call Detail Record (CDR) table, I need to compute the maximum channels that have been simultaneously busy in a specified time range. The table has one column for the end of the call time and another column for the call duration.
CallID DateTime Duration
1 2014-04-28 11:37:54 35
2 2014-04-28 11:37:53 82
3 2014-04-28 11:37:42 53
4 2014-04-28 11:37:37 159
5 2014-04-28 11:37:13 49
6 2014-04-28 11:37:02 267
7 2014-04-28 11:37:00 267
8 2014-04-28 11:36:54 49
9 2014-04-28 11:36:20 266
I would need a report for getting a response like this (time range in hours for example):
DateRange NumBusyChannels
2014-04-28 11:00-12:00 9
2014-04-28 10:00-11:00 5
EDIT: Sample table to test Miky response.
CallID DateTime Duration
014 2013-07-23 08:42:42 3
015 2013-07-23 08:42:42 3
019 2013-07-23 08:42:42 3
012 2013-07-23 08:10:00 3
013 2013-07-23 08:10:00 3
016 2013-07-23 08:10:00 3
017 2013-07-23 08:10:00 3
018 2013-07-23 08:10:00 3

Answer 1

You might start with a query like this which should give you the number of overlapping calls for each call.
SELECT COuter.*,
COALESCE(COverlap.Cnt,0) as NumChannelsInUse
FROM Cdr COuter
LEFT OUTER JOIN(
SELECT C1.CallId,
COUNT(*) as Cnt
FROM Cdr C1
INNER JOIN Cdr C2
ON (C2.DateTime >= C1.DateTime
AND
C2.DateTime <= DATE_ADD(C1.DateTime, INTERVAL C1.Duration SECOND))
OR
(DATE_ADD(C2.DateTime, INTERVAL C2.Duration SECOND) >= C1.DateTime
AND
DATE_ADD(C2.DateTime, INTERVAL C2.Duration SECOND) <= DATE_ADD(C1.DateTime, INTERVAL C1.Duration SECOND))
OR
(C1.DateTime >= C2.DateTime
AND
C1.DateTime <= DATE_ADD(C2.DateTime, INTERVAL C2.Duration SECOND) )
OR
(DATE_ADD(C1.DateTime, INTERVAL C1.Duration SECOND) >= C2.DateTime
AND
DATE_ADD(C1.DateTime, INTERVAL C1.Duration SECOND) < DATE_ADD(C2.DateTime, INTERVAL C2.Duration SECOND))
GROUP BY C1.CallId) COverlap
ON COuter.CallId = COverlap.CallId
You would then have to further manipulate the query to partition the results by hour and then to select the maximum for each hour..