From: | Vik Fearing <vik(at)postgresfriends(dot)org> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | pgsql-bugs <pgsql-bugs(at)postgresql(dot)org> |
Subject: | Re: Wrong result with constant quals |
Date: | 2022-11-03 23:56:56 |
Message-ID: | 309137b4-9b48-5952-c6e1-0fa7007d0419@postgresfriends.org |
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Lists: | pgsql-bugs |
On 11/4/22 00:36, Tom Lane wrote:
> Vik Fearing <vik(at)postgresfriends(dot)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>:
SQL92? wut?
> 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.
I allowed for this by saying it could be a single group with no rows if
you preferred to look at it that way.
This does not explain why the WHERE FALSE is being ignored and producing
rows.
--
Vik Fearing
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