>select anything from a inner join b on a.field=b.field and a.field>0 where a.field>0 into anything
>
>Of course, it is not a problem when the number of filtered records are relativly little.
>
>But a two big (?) 10M, inner joined table produced me an INSUFFICIENT DISK SPACE error message. (It produced a +150M intermediate cursor and 25 sec run time)

Bela, you could try doing this as two selects: do the first one to filter table a, and then join the filtered tables.