Обсуждение: 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=>
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=>
On Thu, Jul 25, 2013 at 10:45 AM, Gary Stainburn <gary.stainburn@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;
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;
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-owner@postgresql.org <pgsql-sql-owner@postgresql.org> on behalf of Gary Stainburn <gary.stainburn@ringways.co.uk> 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
>________________________________________ >Von: pgsql-sql-owner@postgresql.org [pgsql-sql-owner@postgresql.org]" im Auftrag von "Venky >Kandaswamy [venky@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-owner@postgresql.org <pgsql-sql-owner@postgresql.org> on behalf of Gary Stainburn <gary.stainburn@ringways.co.uk> 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
Sorry, but I never thought. I'm developing this on my server I'm developing it for someone else who wants it in a WordPress / MySQL environment (I don't know MySQL). Would this or something similar work in mysql? (Sorry for going O.T.) On Thursday 25 July 2013 19:53:06 Marc Mamin wrote: > >________________________________________ > >Von: pgsql-sql-owner@postgresql.org [pgsql-sql-owner@postgresql.org]" > > im Auftrag von "Venky >Kandaswamy [venky@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 > -- Gary Stainburn Group I.T. Manager Ringways Garages http://www.ringways.co.uk