Re: problem with the sum function

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Marco Kienzle <m(dot)kienzle(at)marlab(dot)ac(dot)uk>
Cc: pgsql-bugs(at)postgresql(dot)org
Subject: Re: problem with the sum function
Date: 2002-05-07 14:37:56
Message-ID: 23443.1020782276@sss.pgh.pa.us
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Marco Kienzle <m(dot)kienzle(at)marlab(dot)ac(dot)uk> writes:
> herring=3D# select sum(agenum) from age where weightmeanage>0 and lengthcel=
> l=3D160;
> sum=20
> -----
> 77
> (1 row)

> select INTO TABLE temp1 inst, year, month, lengthcell, sex, age, agenum, w=
> eightmeanage from age where weightmeanage>0 and lengthcell=3D160 group by i=
> nst, year, month, lengthcell, sex,age,agenum, weightmeanage;

> herring=3D# select sum(agenum) from temp1;
> sum=20
> -----
> 73
> (1 row)

Why would you expect these to give the same result? The "group by"
effectively eliminates duplicate rows, thus removing some contributions
to the sum.

regards, tom lane

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