Re: Group By and wildcards...

From: Bruno Wolff III <bruno(at)wolff(dot)to>
To: Oisin Glynn <me(at)oisinglynn(dot)com>
Cc: Jon Lapham <lapham(at)jandr(dot)org>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-general(at)postgresql(dot)org
Subject: Re: Group By and wildcards...
Date: 2005-02-19 19:20:33
Message-ID: 20050219192033.GA24244@wolff.to
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On Sat, Feb 19, 2005 at 14:02:34 -0500,
Oisin Glynn <me(at)oisinglynn(dot)com> wrote:
>
> But the where clause defines the result of the aggregate function (in this
> case the SUM)?

Not really.

> Is the only reason for needing the GROUP BY CLAUSE is because the aggregate
> function demands it?

Note that there is also a join to a table d. So that values in d are
being summed up based on some connection from d to the other 3 tables.

> If so could something like the following work where we pass the where clause
> conditions into the function and it performs the aggregate function and
> returns.. I am guessing this would be extremely inefficient?
>
> select A.*,B.*,C.*,my_cheating_sum(a.id,b.id,c.id) from a,b,c,
> where some conditions;

If that function did a select from d, you could make this work, but it
would likely be much slower than doing it in one SQL statement.

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