| 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 |
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| 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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