http://stackoverflow.com/questions/4342370/grouping-into-interval-of-5-minutes-within-a-time-range http://stackoverflow.com/questions/4342370/grouping-into-interval-of-5-minutes-within-a-time-range
I have a table which logs events and stores their timestamps (as datetime). I need to be able to break up time into chunks and get number of events that occurred in that interval. The interval can be custom (Say from 5 minutes to 1 hour and even beyond).
The obvious solution is to convert the datetime to unix_timestamp divide it by number of seconds in the interval, take its floor function and multiply it back by the number of seconds. Finally convert the unix_timestamp back to the datetime format.
This works fine for small intervals.
select from_unixtime(floor(unix_timestamp(event.timestamp)/300)*300) as start_time, count(*) as total from event where timestamp>= 2012-08-03 00:00:00 group by start_time;
This gives the correct output
+---------------------+-------+ | start_time | total | +---------------------+-------+ | 2012-08-03 00:00:00 | 11 | | 2012-08-03 00:05:00 | 4 | | 2012-08-03 00:10:00 | 4 | | 2012-08-03 00:15:00 | 7 | | 2012-08-03 00:20:00 | 8 | | 2012-08-03 00:25:00 | 1 | | 2012-08-03 00:30:00 | 1 | | 2012-08-03 00:35:00 | 3 | | 2012-08-03 00:40:00 | 3 | | 2012-08-03 00:45:00 | 5 | ~~~~~OUTPUT SNIPPED~~~~~~~~~~~~
But if I increase the interval to say 1 hour (3600 sec)
mysql> select from_unixtime(floor(unix_timestamp(event.timestamp)/3600)*3600) as start_time, count(*) as total from event where timestamp>= 2012-08-03 00:00:00 group by start_time; +---------------------+-------+ | start_time | total | +---------------------+-------+ | 2012-08-02 23:30:00 | 35 | | 2012-08-03 00:30:00 | 30 | | 2012-08-03 01:30:00 | 12 | | 2012-08-03 02:30:00 | 18 | | 2012-08-03 03:30:00 | 12 | | 2012-08-03 04:30:00 | 4 | | 2012-08-03 05:30:00 | 3 | | 2012-08-03 06:30:00 | 13 | | 2012-08-03 07:30:00 | 269 | | 2012-08-03 08:30:00 | 681 | | 2012-08-03 09:30:00 | 1523 | | 2012-08-03 10:30:00 | 911 | +---------------------+-------+
The reason, as far as I could gauge, for the boundaries not being set properly is that unix_timestamp will convert time from my local timezone (GMT + 0530) to UTC and then output the numerical value.
So a value like 2012-08-03 00:00:00 will actually be 2012-08-02 18:30:00. Dividing and using floor will set the minutes part to 00. But when I use from_unixtime, it will convert it back to GMT + 0530 and hence give me intervals that begin at 30 mins.
How do I ensure the query works correctly irrespective of the timezone? I use MySQL 5.1.52 so to_seconds() is not available
EDIT:
The query should also fire correctly irrespective of the interval (can be hours, minutes, days). A generic solution would be appreciated