From what I understand is:
1) you will have categories
2) and subcategories that will belong to the categories
3) and you will have businesses that may or may not belong to a
subcategory but will definitely belong to a category
if this is what you want then you will have to change your categories,
subcategories and businsesses table.
This will also result in changing your models for these tables.
Logically a business would belong to a subcategory which in turn would
belong to a category, ie a category can have many subcategories as
well as businesses and a subcategory can have many businesses.
Correct me if I am wrong?