From: Tom Lane <tgl@sss.pgh.pa.us>
To: Vik Fearing <vik@postgresfriends.org>
Cc: pgsql-bugs <pgsql-bugs@postgresql.org>
Subject: Re: Wrong result with constant quals
Date: Thu, 03 Nov 2022 19:36:20 -0400
Message-ID: <2193245.1667518580@sss.pgh.pa.us> (raw)
In-Reply-To: <f895925a-f2da-5651-af71-21cd8238b9f5@postgresfriends.org>
References: <f895925a-f2da-5651-af71-21cd8238b9f5@postgresfriends.org>
Vik Fearing <vik@postgresfriends.org> writes:
> The following query returns a wrong result, in my opinion.
> postgres=# select 1 where false having true;
> ?column?
> ----------
> 1
> (1 row)
> The correct result should be zero rows.
No, I don't think so. The presence of HAVING without GROUP BY makes
this act like a query with an aggregate function and no GROUP BY: you
get a single grouped row, regardless of what the input is. There's a
reasonably clear specification of that in SQL92 7.8 <having clause>:
1) Let T be the result of the preceding <from clause>, <where
clause>, or <group by clause>. If that clause is not a <group
by clause>, then T consists of a single group and does not have
a grouping column.
"A single group" is not "no groups".
Later SQL versions define this by reference to "GROUP BY ()", but
I think the effect is the same.
regards, tom lane
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To: pgsql-bugs@postgresql.org
Cc: tgl@sss.pgh.pa.us, vik@postgresfriends.org
Subject: Re: Wrong result with constant quals
In-Reply-To: <2193245.1667518580@sss.pgh.pa.us>
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