Subject A complicated subquery slows down the main query
Author Maciek BOROWKA

I have a problem with the performance of some of the queries I do.
They are all basically of the same type:

SELECT * from Atable WHERE AKey IN
(select aKey
from AnotherTable
group by aKey
having count(*) > 1)

As you can see, I need to make a complicated subquery and then
use it in a join to select some other data. An important point is
that my subquery is not related to the main one (I mean, no
common parameters). However, as far as I understand, firebird
will execute the subquery for every row in the query in order
to verify the "IN" condition. As you can imagine, everything
is horribly slow (1 minute of a bi-xeon server) and thus quite
My question is : what is a "firebirdish" way of achieving the wanted
result? I tried to create a view with the subquery but the problem
is the same.

It's firebird 1.0.3, by the way. I didn't check it with 1.5.

Best regards,
Maciek Borowka