> Though, thinking about it Dimitry, it is possible without WITH (and
> hence, with older Firebird versions) through using subselects:

If Firebird is not so old, I think it is also possible with SELECT
FROM SELECT. Something like this:

select a.col1, a.total1, b.total2 from
(select cola1 as col1, sum(cola2) as total1 from tablea group by 1) a
full join
(select colb1 as col1, sum(colb2) as total2 from tableb group by 1) b
on a.col1=b.col1

Forgive me if I'm wrong again.

SY, SD.