When i try to run the query below (using IBExpert and FB 1.5), the
parameter is calculated as a char(3), probably because the second
comparision ( = 'all' ). I expected the parameter to be calculated
as varchar(15), as the column a.first_name. Is this behavior
expected?

select
a.*
from
employee a
where
a.first_name = :first_name or :first_name = 'all'

Thanks.