From: Richard Broersma Jr <rabroersma@yahoo.com>
To: operationsengineer1@yahoo.com, "pgsql-sql@postgresql.org" <pgsql-sql@postgresql.org>
Subject: Re: How To Exclude True Values
Date: Tue, 6 Jun 2006 16:40:31 -0700 (PDT)
Message-ID: <20060606234031.168.qmail@web31807.mail.mud.yahoo.com> (raw)
In-Reply-To: <20060606230141.3017.qmail@web33310.mail.mud.yahoo.com>
> Richard, that is the result i would need given that
> data set. i have to digest this version, though.
>
> should this query be more efficient than the subquery
> version as the table starts to get large?
My experience is that Distinct On queries do not preform as well as their group by counter parts.
I believe that others have also commented to the same effect.
To speed the query you could apply indexes on the group by fields and the join columns.
Also, I produced a second query using PostgreSQL:
select a.id_i, a.ir_id, a.test, a.stamp
from test a
join
(
select max(stamp) as mstamp, id_i
from test
group by id_i
) b
on a.stamp = b.mstamp
where a.test = false
;
-- result
id_i | ir_id | test | stamp
------+-------+------+---------------------
4 | 8 | f | 2006-06-05 08:00:00
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To: pgsql-sql@postgresql.org
Cc: rabroersma@yahoo.com
Subject: Re: How To Exclude True Values
In-Reply-To: <20060606234031.168.qmail@web31807.mail.mud.yahoo.com>
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