Hi,
this is up to your search script, if user let "Please select" option then you will get a 0 as selected id.
So you have Make=make12 Model=model235 and Year=0. What you need is to check $_POST['Year'] if is 0 to exclude that field from where clause,
select * from spare_parts where make='make12' and model='model235'
instead of quering
select * from spare_parts where make='make12' and model='model235' and year=0
that's what i think
