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Re: Improving GROUP BY?

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Peter Eisentraut <peter_e(at)gmx(dot)net>
Cc: Oliver Siegmar <oliver(at)siegmar(dot)net>, pgsql-general(at)postgresql(dot)org
Subject: Re: Improving GROUP BY?
Date: 2005-09-30 14:00:53
Message-ID: 20398.1128088853@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-general
Peter Eisentraut <peter_e(at)gmx(dot)net> writes:
> Am Freitag, 30. September 2005 09:03 schrieb Oliver Siegmar:
>> - Is this requirement (all fields in GROUP BY) based on the SQL standard?

> What you describe is called "functional dependencies" in the SQL standard.  
> (The query processor would recognize that the non-primary key columns 
> "functionally depend" on the primary key and therefore do not have to be 
> grouped separately.)  This is definitely a valid feature but PostgreSQL does 
> not implement it yet.

Note also that the "functional dependencies" stuff was added in SQL99.
Postgres' current behavior corresponds to the SQL92 standard.

			regards, tom lane

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