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=>
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