Re: [SQL] HAVING in EXISTS-clause ...

Stuart Rison <rison@biochemistry.ucl.ac.uk> writes:
> It's just a case of reversing the order of the aggregate and the constant
> in your qualifier (as hinted to by the error message).

> This worked for me

> SELECT [DISTINCT] AO,AT,AV FROM P3AT AS OAT
> WHERE
>  EXISTS(
>    SELECT AO FROM P3AT
>    WHERE
>      AO = OAT.AO
>    GROUP BY AO
>    HAVING 8 = COUNT(*)
>    );

Marten has actually stumbled across a bug here: the rewriter mistakenly
thinks that COUNT() appears in the outer SELECT's WHERE clause (well,
it does, but since it's inside a sub-select it really belongs to the
inner SELECT) and is trying to rewrite the query to push the COUNT()
into yet a third level of SELECT.  That doesn't hurt in this case, but
in other cases it generates the wrong answer.

The "must be at right side in qual" message appears because the rewriter
only knows how to push down COUNT() on the right side of an operator.
That's a pretty bogus limitation, but the whole thing is really pretty
bogus --- none of that rewriter code would exist if we could handle views
involving aggregate functions as sub-selects in FROM.  So it's probably
not worth any effort to add more code to a routine that shouldn't exist
in the first place; we've got to work on the fundamental problem
instead.
        regards, tom lane