Testing all conditions or params

I’m stuck in a bit of a quandry here. This might be a bad implementation but I’m really after solving just one issue. I’ll hold off getting into the whole thing.
Right now I have a ajax “dynamic” search form. Dynamic meaning users can enter any number of choices in the 5 available fields.

In order to get the conditions correctly and allow for fields not being used I did the following:

unless(params[:category_id]|| “”).empty?

So each field if left unselected is being evaluated with “”

What I’m finding is that if all the fields are deselected in the form, all records are being returned. Not a good thing.
Not sure how to code a coditional here , and effectively , to see if all fields are “”

And then prevent select from taking place.

Stuart