Try this. Once you know the value you want you have to join back to
find the time of that value.
Select f.Lid, F.Value,F.event_id, f.obstime
From (
SELECT lid, MAX(value) As Value, event_id
FROM flood_ts
GROUP BY lid, event_id
)sub
Join flood f On sub.Value=f.value and f.lid=sub.lid and
sub.event_id=v.event_id
-----Original Message-----
From: pgsql-sql-owner@postgresql.org
[mailto:pgsql-sql-owner@postgresql.org] On Behalf Of Mark Fenbers
Sent: Thursday, March 31, 2011 1:15 PM
To: PostgreSQL - SQL
Subject: [SQL] Aggregates puzzle
SQL gurus,
I have a table with 4 columns: lid(varchar), value(float),
obstime(datetime), event_id(integer)
I want to find the MAX(value) and the time and date that it occurred
(obstime) in each group of rows where the lid and event_id are the same.
What I have works correctly in identifying the MAX(value) for the given
group, but I'm having trouble getting the corresponding obstime to be
reported along with it.
Here's the SQL I have:
SELECT lid, MAX(value), event_id
FROM flood_ts
GROUP BY lid, event_id
ORDER BY lid;
If I add "obstime" to the SELECT list, then I need to add "value" to the
GROUP BY clause, which makes the MAX(value) function report *each row*
as a maximum.
So, how can I revise my SQL to report the obstime that the MAX(value)
occurred?
Any help is sincerely appreciated.
Mark
