[SQL] value from max row in group by
Hi folks, I need help please. I have a table of trip section details which includes a trip ID, start time as an offset, and a duration for that section. I need to extract the full trip duration by adding the highest offset to it's duration. I can't simply use sum() on the duation as that would not include standing time. Using the data below I would like to get: 1 | 01:35:00 2 | 01:35:00 3 | 01:06:00 4 | 01:38:00 5 | 01:03:00 6 | 01:06:00 from timetable=> select stts_id, stts_offset, stts_duration from standard_trip_sections order by stts_id, stts_offset; stts_id | stts_offset | stts_duration -+-+--- 1 | 00:00:00| 00:18:00 1 | 00:19:00| 00:26:00 1 | 00:47:00| 00:13:00 1 | 01:13:00| 00:22:00 2 | 00:00:00| 00:18:00 2 | 00:20:00| 00:09:00 2 | 00:29:00| 00:17:00 2 | 00:50:00| 00:13:00 2 | 01:13:00| 00:22:00 3 | 00:00:00| 00:20:00 3 | 00:28:00| 00:15:00 3 | 00:44:00| 00:22:00 3 | 00:48:00| 00:20:00 4 | 00:00:00| 00:20:00 4 | 00:28:00| 00:15:00 4 | 00:48:00| 00:13:00 4 | 01:01:00| 00:13:00 4 | 01:18:00| 00:20:00 5 | 00:00:00| 00:18:00 5 | 00:20:00| 00:09:00 5 | 00:29:00| 00:17:00 5 | 00:50:00| 00:13:00 6 | 00:00:00| 00:15:00 6 | 00:20:00| 00:13:00 6 | 00:33:00| 00:13:00 6 | 00:46:00| 00:20:00 (26 rows) timetable=> -- Sent via pgsql-sql mailing list (pgsql-sql@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-sql
Re: [SQL] value from max row in group by
As usual, once I've asked the question, I find the answer myself. However, it *feels* like there should be a more efficient way. Can anyone comment or suggest a better method? timetable=> select stts_id, stts_offset+stts_duration as total_duration timetable-> from standard_trip_sections timetable-> where (stts_id, stts_offset) in timetable-> (select stts_id, max(stts_offset) from standard_trip_sections group by stts_id); stts_id | total_duration -+ 1 | 01:35:00 2 | 01:35:00 3 | 01:08:00 4 | 01:38:00 5 | 01:03:00 6 | 01:06:00 (6 rows) timetable=> -- Sent via pgsql-sql mailing list (pgsql-sql@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-sql
Re: [SQL] value from max row in group by
On Thu, Jul 25, 2013 at 10:45 AM, Gary Stainburn < gary.stainb...@ringways.co.uk> wrote: > Hi folks, > > I need help please. > > I have a table of trip section details which includes a trip ID, start > time as > an offset, and a duration for that section. > > I need to extract the full trip duration by adding the highest offset to > it's > duration. I can't simply use sum() on the duation as that would not include > standing time. > > Using the data below I would like to get: > > 1 | 01:35:00 > 2 | 01:35:00 > 3 | 01:06:00 > 4 | 01:38:00 > 5 | 01:03:00 > 6 | 01:06:00 > How about using a WINDOW function? Eg. select stts_id, total from (select stts_id, stts_offset+stts_duration as total, row_number() over (partition by stts_id order by stts_offset desc) as rank from sts) s where rank = 1 order by stts_id;
Re: [SQL] value from max row in group by
You can use Postgres WINDOW functions for this in several different ways. For example, one way of doing it: select stts_id, last_value(stts_offset) over (partition by stts_id order by stts_offset desc) + last_value(stts_duration) over (partition by stts_id order by stts_offset desc) from table group by stts_id; Venky Kandaswamy Principal Engineer, Adchemy Inc. 925-200-7124 From: pgsql-sql-ow...@postgresql.org on behalf of Gary Stainburn Sent: Thursday, July 25, 2013 10:57 AM To: pgsql-sql@postgresql.org Subject: Re: [SQL] value from max row in group by As usual, once I've asked the question, I find the answer myself. However, it *feels* like there should be a more efficient way. Can anyone comment or suggest a better method? timetable=> select stts_id, stts_offset+stts_duration as total_duration timetable-> from standard_trip_sections timetable-> where (stts_id, stts_offset) in timetable-> (select stts_id, max(stts_offset) from standard_trip_sections group by stts_id); stts_id | total_duration -+ 1 | 01:35:00 2 | 01:35:00 3 | 01:08:00 4 | 01:38:00 5 | 01:03:00 6 | 01:06:00 (6 rows) timetable=> -- Sent via pgsql-sql mailing list (pgsql-sql@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-sql -- Sent via pgsql-sql mailing list (pgsql-sql@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-sql
Re: [SQL] value from max row in group by
> >Von: pgsql-sql-ow...@postgresql.org [pgsql-sql-ow...@postgresql.org]" im >Auftrag von "Venky >Kandaswamy [ve...@adchemy.com] > >You can use Postgres WINDOW functions for this in several different ways. For >example, one way of doing it: > >select stts_id, last_value(stts_offset) over (partition by stts_id order by >stts_offset desc) > + last_value(stts_duration) over (partition by stts_id order > by stts_offset desc) >from table >group by stts_id; another simple solution with distinct on: select distinct on (stts_id, stts_offset) stts_id, stts_offset+stts_duration from table order by stts_id, stts_offset desc Marc Mamin From: pgsql-sql-ow...@postgresql.org on behalf of Gary Stainburn Sent: Thursday, July 25, 2013 10:57 AM To: pgsql-sql@postgresql.org Subject: Re: [SQL] value from max row in group by As usual, once I've asked the question, I find the answer myself. However, it *feels* like there should be a more efficient way. Can anyone comment or suggest a better method? timetable=> select stts_id, stts_offset+stts_duration as total_duration timetable-> from standard_trip_sections timetable-> where (stts_id, stts_offset) in timetable-> (select stts_id, max(stts_offset) from standard_trip_sections group by stts_id); stts_id | total_duration -+ 1 | 01:35:00 2 | 01:35:00 3 | 01:08:00 4 | 01:38:00 5 | 01:03:00 6 | 01:06:00 (6 rows) timetable=> -- Sent via pgsql-sql mailing list (pgsql-sql@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-sql -- Sent via pgsql-sql mailing list (pgsql-sql@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-sql -- Sent via pgsql-sql mailing list (pgsql-sql@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-sql
