I've been looking on the net for a soultion to a problem, and seem to be
missing something in firebird...

The situation is I have two tables of items (say A and B). A third table
lists groups each item belongs to (G), where A and B may have multiple
references in G.

I want a query that, given a member of A, returns a list of all of B
that belong to any group A is a member of.

Now looking on the net, I see 'intersection' as a keyword that isn't
supported in FB, so I presume some other approach is used. Can anyone
point me to a reference that addresses this?

I've tried using the 'in' function, but that gives 'multiple records in
singleton query' kinds of problems...

Thanks,
Terry