> name BETWEEN 'A' AND 'D'
>
> is the same as
>
> name >= 'A' AND name <= 'D'
>
> If the optimizer does a good job (Firebird 1.0.2 works OK, haven't
> checked other versions), there should be no difference in performance
> between the two.

There is no BETWEEN verb in BLR, it means the former expression
is internally converted to the latter in early stages of processing,
and optimizer get identical request in both cases.
(i.e. the result does not depend on whether optimizer does a good job or not)

Ivan