> > > select *
> > > from tabA
> > > where col1 = (select col2
> > > from tabB
> > > where tabA.col3 = tabB.col4
> > > and exists (select *
> > > from tabC
> > > where tabB.colX = tabC.colX and
> > > tabC.colY = tabA.col2)
> > > )
I checked this in Informix, it works.
Andreas