In a bookstore database, if the items to be sold are stored in separate "category" tables such as "School Supplies", "Books", "Apparel".  How do I relate them ALL to an "ORDERS" table (junction between customer and the products) It seems if I used BookID, ApparelID and SupplyID than I have too many blank entries in my junction table if a customer doesn't order one of each category.  I'm splitting them into categories so that the relevant attributes for each can be stored (IE books don't need a SIZE and Color, but Apparel does)

---

Reply from Richard Rost:

Each Product has a CategoryID as a foreign key. Simple one-to-many relationship. Each order has an order details table for the line items. Each order detail record has a ProductID. If you know the ProductID you can look up the CategoryID. I cover this in Access Expert 3. Don't skip 1 and 2. Those have the fundamentals of relationships.