"Jaime Casanova" <el_vigia_ec(at)hotmail(dot)com> writes:
> brings 'A ', 'B ', 'C ' well when i cHange the real query
Given that you spelled it like that, I wonder whether you aren't
confused about the behavior of cross-data-type comparisons. If
one column is char(n) and the other is text or varchar(n) then you
may get results you didn't expect. These types have different ideas
about whether trailing blanks are significant or not.
regards, tom lane