Obviously I am being dense today, but I still cannot see why changing the order of the 2 expressions changes the results.

select ... where (a.fld2a=b.fld2b) AND (trim(a.fld1a)=trim(b.fld1b))

and

select ... where (trim(a.fld1a)=trim(b.fld1b)) AND (a.fld2a=b.fld2b)

really ought to give the same results & the results should be consistent regardless of setting ansi (I know setting it to on affects the results & leads to consistent results, but even if off the results should be consistent).

I described the problem somewhere as asking for a list of all people called Len and having fair & then asking for a list of all people with fair hair and called Len. Would you (intuitively) expect to get different results ?