On Wed, Apr 10, 2013 at 12:30 PM, Steve Crawford < scrawf...@pinpointresearch.com> wrote:
> I'm seeking ideas on the best way to craft the following query. I've > stripped everything down to the bare essentials and simplified it below. > > Input data has a timestamp (actually an int received from the system in > the form of a Unix epoch), a unit identifier and a status: > > event_time | unit_id | status > ------------+---------+-------**- > 1357056011 | 60 | 1 > 1357056012 | 178 | 0 > 1357056019 | 168 | 0 > 1357056021 | 3 | 0 > 1357056021 | 4 | 1 > 1357056021 | 179 | 0 > 1357056022 | 0 | 1 > 1357056022 | 1 | 0 > 1357056023 | 2 | 0 > 1357056024 | 9 | 0 > 1357056025 | 5 | 0 > 1357056025 | 6 | 0 > 1357056026 | 7 | 1 > ... > > A given unit_id cannot have two events at the same time (enforced by > constraints). > > Given a point in time I would like to: > > 1. Identify all distinct unit_ids with an entry that exists in the > preceding hour then > > 2. Count both the total events and sum the status=1 events for the most > recent 50 events for each unit_id that fall within a limited period (e.g. > don't look at data earlier than midnight). So unit_id 60 might have 50 > events in the last 15 minutes while unit_id 4 might have only 12 events > after midnight. > > The output would look something like: > > unit_id | events | status_1_count > ---------+--------+-----------**----- > 1 | 50 | 34 > 2 | 27 | 18 > 1 | 50 | 34 > 1 | 2 | 0 > ... > > Each sub-portion is easy and while I could use external processing or > set-returning functions I was hoping first to find the secret-sauce to glue > everything together into a single query. > > Cheers, > Steve > > > something like select unit_id, count(*), sum(status) from mytable a where event_time >= [whatever unix epoch translates to "last midnight"] and exists ( select * from mytable b where b.unit_id = a.unit_id and b.epoch >= [unix epoch that translates to "one hour ago"]) group by unit _id; 1) I think figuring out the unix epoch should be reasonable...but I don't know how to do it off the top of my head. 2) I could completely be misunderstanding this. I'm not sure why the example results would have unit id 1 repeated. (which my suggestion WON'T do)
