Re: value from max row in group by

>________________________________________
>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=>


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