On Jul 27, 2010, at 7:12 PM, Dann Corbit wrote:
I have a table containing events with timestamps. I would like
to generate a histogram of the number of each type of event for each
half-hour period from 8:00 am to 6:00 pm. Are there any tools that
will help me do this?
GROUP BY is essentially a histogram generator.
The age() function will give you an interval.
I am not sure if you want to combine half hour periods from different days with the same time or not (IOW are 8AM Tuesday and 8AM Wednesday supposed to be grouped together or not?)
I guess that if you are more specific about exactly what you want you can get a better answer. Your requirement is a little bit vague or ambiguous.
I don't mind using Excel to generate the actual graphic. Ideally I'd get output something like this:
date start end event count
---------- -------- -------- -------- -----
2010-07-27 08:00:00 08:29:59 EVENT_1 20
2010-07-27 08:00:00 08:29:59 EVENT_2 15
2010-07-27 08:30:00 08:59:59 EVENT_1 10
2010-07-27 08:30:00 08:59:59 EVENT_3 5
I'm quite familiar with SQL, but I'm not sure how to generate the half hour intervals without hard coding them.
Thanks,
Patrick