From: Josh Berkus <josh@agliodbs.com>
To: David Siegal <dsiegal@brave.cs.uml.edu>
Cc: pgsql-sql@postgresql.org
Subject: Re: Calculating Percentages
Date: Wed, 14 May 2003 08:24:35 -0700
Message-ID: <200305140824.35328.josh@agliodbs.com> (raw)
In-Reply-To: <Pine.LNX.4.44.0305081102100.30051-100000@brave.cs.uml.edu>
References: <Pine.LNX.4.44.0305081102100.30051-100000@brave.cs.uml.edu>
David,
> If I were to do:
> SELECT nationality, ((COUNT(*) * 100)/(select count(*) from member)) as
> percentage FROM member GROUP BY nationality ORDER BY nationality;
>
> would this repeatedly execute the inner query over and over?
Yes, it would
Better is:
SELECT nationality, (COUNT(*)*100/total_members) as percentage
FROM member,
(SELECT COUNT(*) as total_members FROM members) tot_mem
GROUP BY nationality
ORDER BY nationality
This method runs the grand total only once.
--
Josh Berkus
Aglio Database Solutions
San Francisco
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To: pgsql-sql@postgresql.org
Cc: josh@agliodbs.com, dsiegal@brave.cs.uml.edu
Subject: Re: Calculating Percentages
In-Reply-To: <200305140824.35328.josh@agliodbs.com>
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