From: Josh Berkus <josh@agliodbs.com>
To: Tomasz Myrta <jasiek@klaster.net>
To: Robert Treat <xzilla@users.sourceforge.net>
To: pgsql-sql@postgresql.org
Subject: Re: can i make this sql query more efficiant?
Date: Fri, 4 Apr 2003 08:16:01 -0800
Message-ID: <200304040816.01369.josh@agliodbs.com> (raw)
In-Reply-To: <20030404080209.M3259@klaster.net>
References: <1049403724.13799.5473.camel@camel>
<20030404080209.M3259@klaster.net>
Tomasz,
> What about this:
> select
> event,
> sum(case when level=1 then 1 else 0 end) as ones,
> sum(case when level=2 then 1 else 0 end) as twos,
> sum(case when level=3 then 1 else 0 end) as threes
> from baz
> group by event;
That version is only more efficient for small data sets. I've generally
found that case statements are slower than subselects for large data sets.
YMMV.
BTW, while it won't be faster, Joe Conway's crosstab function in /tablefunc
does this kind of transformation.
--
Josh Berkus
Aglio Database Solutions
San Francisco
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To: pgsql-sql@postgresql.org
Cc: josh@agliodbs.com, jasiek@klaster.net, xzilla@users.sourceforge.net
Subject: Re: can i make this sql query more efficiant?
In-Reply-To: <200304040816.01369.josh@agliodbs.com>
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