Re: 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-owner(at)postgresql(dot)org <pgsql-sql-owner(at)postgresql(dot)org> on behalf of Gary Stainburn <gary(dot)stainburn(at)ringways(dot)co(dot)uk>
Sent: Thursday, July 25, 2013 10:57 AM
To: pgsql-sql(at)postgresql(dot)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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