Re: WHERE on an alias

Joseph,

> playpen=# select a, sum(b) as dsum from taba where dsum > 5 group
> by(a);
> ERROR:  Attribute 'dsum' not found
> 
> Why can we GROUP BY on an alias but not do a WHERE on an alias?  I
> have a subselect that 
> explain shows is being run twice if I have to put it in the WHERE
> clause.

Ah, but you are not trying to do a WHERE on an alias ... you are trying
to do a WHERE on an *aggregate*, which is a different thing.  Consult
your favorite SQL manual; the construction you want is:

SELECT a, sum(b) as dsum 
FROM taba
GROUP BY a
HAVING dsum > 5;

-Josh Berkus

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