Message-ID: <25b70e6ec7bef81acac508dc61dfa01e72c96252.camel@cybertec.at>
Subject: Re: group by can use alias from select list
From: Laurenz Albe <laurenz.albe@cybertec.at>
To: postgres-hape@gmx.de, pgsql-docs@lists.postgresql.org
Date: Tue, 11 Jul 2023 16:19:48 +0200
In-Reply-To: <168871536004.379168.9352636188330923805@wrigleys.postgresql.org>
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On Fri, 2023-07-07 at 07:36 +0000, PG Doc comments form wrote:
> i have a discussion in pgsql-bugs@lists.postgresql.org=C2=A0about this an=
d it is
> mentioned in the answers that it is documented and a "feature" of Postgre=
s
> that this can be done.
> If this is wanted the documentation
> (https://www.postgresql.org/docs/current/sql-select.html) that mentioned:
> [execution order of SELECT that says that GROUP BY is before SELECT]
> isn't correct because how=C2=A0 can 4.) be done and the alias from 5.) is=
 used?
> Here is a hint important that there is an exception for alias used in gro=
up
> by

I think that is already documented:

> An expression used inside a grouping_element can be an input column name,
> or the name or ordinal number of an output column (SELECT list item),
> or an arbitrary expression formed from input-column values.

An alias in this case would be an output column.  Perhaps we can mention
the alias explicitly.

Yours,
Laurenz Albe