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Date: Wed, 21 Oct 2009 14:16:08 +0200
From: "A. Kretschmer" <andreas.kretschmer@schollglas.com>
To: pgsql-sql@postgresql.org
Subject: Re: report generation from table.
Message-ID: <20091021121607.GA1086@a-kretschmer.de>
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In response to sathiya psql :
> Hi All,
> 
> I have been searching for, Preparing report from a huge table.
> 
> Queries am executing now are,
> SELECT count(*) from HUGE_TBL where cond1, cond2;
> SELECT count(*) from HUGE_TBL where cond1, cond3;
> --- like this i have different conditions(10-15 different things ) and
> different amount of conditions ( 2 - 5 condition ).
> 
> As that is a very huge table, it took time to execute each query ( 2 min ). And
> finally it takes 15 times that ( 30 min ).  Is there anyway to do the above
> report efficiently ?
> 
> Such executing the query only once, and getting all different outputs required
> ? or fetching result from some cache ?

select sum(case when <cond1> and <cond2> then 1 else 0 end) as query1,
sum(case when <cond1> and <cond3> then 1 else 0 end) as query2, ... from
table;


It forces a whole seq. scan, but only once.


Regards, Andreas
-- 
Andreas Kretschmer
Kontakt:  Heynitz: 035242/47150,   D1: 0160/7141639 (mehr: -> Header)