Complex table/query

I have the following info to store in a DB:

[1] Keep a record of category items as well as owner name, street, state,
zip..etc ....

[2] Keep a running tab on the number of items overall in the DB

[3] Keep a running tab on the number of items overall in the DB by state.

I am allowing the viewer to first select the state and then the city and finally
the category. Once they arrive at the category page I want to show them the
number of items that are in the DB for that state, city and category.

I am using PHP/Postgres to make a <select></select> statement that will show the
categories, of which there are around 115. The obvious 50 states....

I can build this ridulious SQL statement that just eats the hell out of the
processor.

Does anyone have any ideas how I can query/build this thing?

Thanks

Andy