many thanks to all for your help on this. the qualified field name in the
order by clause did in fact solve it for me. along the way i was confused
(and then posted my confusions) due to forgetting that i used the same
qualified order by clause in several other datasets where table aliases had
not been used. as usual, reducing the problem down to simple test tables and
selects, then monitoring the application sql showed it up. once again thanks
for your time.

Kind regards,
Pete Bray