[mapserver-users] mapfile filter & variable substitution question

[Jennifer Shanks]

Hi,

I have a question about using the mapfile Filter option with variable 
substitution.  In my user interface (OpenLayers), I have drop down boxes 
that allow users to filter the data display based on selected year and 
selected category.  Accordingly, I have two filters set up in my mapfile: 

  FILTER "year = %selected_year%" 
  FILTER "category=%selected_category%" 

What if the user wants to see data for all years or for all categories?  
Is there a way that I can submit a wildcard in my mapserv URL instead?  
Or is there some other way to do this?  My data source is a PostGIS.

Regards,
Jennifer