On 11/4/22 00:36, Tom Lane wrote:
> 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>:
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
