Jeff,

Firebird doesn't order the tables, if by that you mean moving
data around on disk. It orders the results in memory. That's
remarkably fast compared to reading disk blocks. The problem
with the "read in index order" is that it often must read one
record from over here, the next from over there, etc. Sorting
100,000 records can take a while. Sorting a plausible number
to return does not.

Good luck,

Ann