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From: David G. Johnston <[email protected]>
To: Adrian Klaver <[email protected]>
Cc: PALAYRET Jacques <[email protected]>
Cc: [email protected]
Subject: Re: PostgreSQL query with FULL OUTER JOIN and subquery using column of GROUP BY expression ERROR: subquery uses ungrouped column from outer query
Date: Wed, 25 Feb 2026 09:20:18 -0700
Message-ID: <CAKFQuwY27TZSERWdmC+=RO+B86KAOSW+CeJSSL52eUZQLYZsrA@mail.gmail.com> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
	<[email protected]>

On Wed, Feb 25, 2026 at 9:00 AM Adrian Klaver <[email protected]>
wrote:

> 1) Why FROM (SELECT * FROM t1 ) AS t1 instead of just FROM t1?
>     Same for JOIN (SELECT * FROM t3   ) t3
>

Seems immaterial.  It's just a consequence of simplifying the original
problem query. If it is consequential that would seem buggy.


> 2) Why are the field names not table qualified e.g. t2.id, t3.id, etc?
>

Because of the USING clause, those references shouldn't exist in the main
query.


> 3) What is the desired outcome?
>

For the engine to realize the 'id' in the group by and the 'id' in the
scalar subquery are the same 'id' - the one produced by the USING clause,
not either of the t2 or t3 ids.

My first impression is that this is a bug.  Especially since the query
apparently executes in both left-join and right-join modes.

David J.

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  Subject: Re: PostgreSQL query with FULL OUTER JOIN and subquery using column of GROUP BY expression ERROR: subquery uses ungrouped column from outer query
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