On Tuesday, March 17, 2015, Israel Brewster <isr...@ravnalaska.net> wrote:
> > > > On Mar 17, 2015, at 8:09 AM, Paul Jungwirth <p...@illuminatedcomputing.com > <javascript:;>> wrote: > > > >>> test=> select h, count(*) from start_end, generate_series(0, 23) as > s(h) where h between extract(hour from start_time) and extract(hour from > end_time) group by h order by h; > >>> > >>> h | count > >>> ----+------- > >>> 8 | 2 > >>> 9 | 3 > >>> 10 | 2 > >>> 11 | 2 > > > > Note if you always want all 24 rows with a count of 0 when appropriate > (which seems common in reports with tables or plots), you can just tweak > the above query to use a left join: FROM generate_series(0, 23) AS s(h) > LEFT OUTER JOIN start_end ON h BETWEEN ... > > > > Paul > > Right, thanks. That makes sense. So next question: how do I get the > "active" time per hour from this? To use the same example that came up with > this result set: > Which is why you do not (only?) want to convert your data to hour-of-day but want to create timestamp end points. Then you simply do timestamp subtraction to get durations which you can then sum together. David J.
