There can be five tables in database:
CATEGORY this table stores information about products categories of your store and categories hierarchy.
parent field of this table stores ID of the parent category.
PRODUCT all products of your store are stored in this table. This table has a foreign key categoryID which identifies ID of the category to which a product belongs.
ORDER this table stores information about all orders made by visitors of your store.
ORDERED_SHOPPING_CART table is tightly connected with PRODUCT and ORDER tables; stores information on customers' orders content.
SPECIAL_OFFER table contains a list of products, which are shown on home page as special offers
