Re: Group by range in hour of day

> On Mar 17, 2015, at 8:09 AM, Paul Jungwirth <pj(at)illuminatedcomputing(dot)com> 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:

Given this:

test=> select * from start_end ;
id | start_time | end_time
----+------------------------+------------------------
1 | 2015-03-16 08:15:00-07 | 2015-03-16 09:35:00-07
2 | 2015-03-16 09:15:00-07 | 2015-03-16 11:05:00-07
3 | 2015-03-16 08:00:00-07 | 2015-03-16 11:45:00-07

The specified query returns this:

h | count
----+-------
8 | 2
9 | 3
10 | 2
11 | 2

Which is an excellent start, but I also need one more column, which is the total "active" time per hour. So given the intermediate result of this:

id | start_time | end_time | h
----+------------------------+------------------------+----
1 | 2015-03-16 08:15:00-07 | 2015-03-16 09:35:00-07 | 8
3 | 2015-03-16 08:00:00-07 | 2015-03-16 11:45:00-07 | 8
1 | 2015-03-16 08:15:00-07 | 2015-03-16 09:35:00-07 | 9
2 | 2015-03-16 09:15:00-07 | 2015-03-16 11:05:00-07 | 9
3 | 2015-03-16 08:00:00-07 | 2015-03-16 11:45:00-07 | 9
2 | 2015-03-16 09:15:00-07 | 2015-03-16 11:05:00-07 | 10
3 | 2015-03-16 08:00:00-07 | 2015-03-16 11:45:00-07 | 10
2 | 2015-03-16 09:15:00-07 | 2015-03-16 11:05:00-07 | 11
3 | 2015-03-16 08:00:00-07 | 2015-03-16 11:45:00-07 | 11

I'd want a final result of this:

h | count | sum
----+---------------
8 | 2 | 1.75 (or 1:45:00 or whatever)
9 | 3 | 2.33 (2:20:00)
10 | 2 | 2.00 (2:00:00)
11 | 2 | 0.83 (0:50:00)

Where the 1:45 in the 8 hour is based on 45 minutes from row id 1 [8:15-9:00) plus the full hour [08:00-9:00) from row id 3, the hour 9 value is based on the amount of rows 1,2 and 3 that fall within the 9 hour, etc.
-----------------------------------------------
Israel Brewster
Systems Analyst II
Ravn Alaska
5245 Airport Industrial Rd
Fairbanks, AK 99709
(907) 450-7293
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