> And there is the general solution considering null-fields:
> where (field = coalesce( :var, field))
> or (coalesce( :var, field) is null))
>

Christian,

This is an excellent solution. In fact a few minutes ago I was
pondering this problem and wondered whether coalesce could be employed
to solve it.

Of course it would require FB 1.5 or higher for Coalesce.

Adam