Date: Sat, 16 Oct 2021 11:59:15 -0300
From: Alvaro Herrera <alvherre@alvh.no-ip.org>
To: kyle@lahnakoski.com, pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #17232: DISTINCT ON does not allow AS
Message-ID: <202110161459.hufnhzw4bosn@alvherre.pgsql>
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On 2021-Oct-15, PG Bug reporting form wrote:

> The following SQL has an unexpected syntax error
> 
>     SELECT DISTINCT ON (col) AS col, col2 FROM test

Well, the "ON (col)" part is not an output column -- it's just the
specification of the column that you want distinctness over.  I suspect
you mean 

SELECT DISTINCT ON (col) col AS col, col2 FROM test

... which looks like a pretty bogus thing to do, since you have no say
on *which* values of col2 are you going to get for each distinct value
of col.  But ... it gives *some* result, at least.

-- 
Álvaro Herrera         PostgreSQL Developer  —  https://www.EnterpriseDB.com/
"Pensar que el espectro que vemos es ilusorio no lo despoja de espanto,
sólo le suma el nuevo terror de la locura" (Perelandra, C.S. Lewis)