After going through the GSG, it never addresses the issue of storing the billing information (including customer name, e-mail address, phone number, etc.). I know I can just store the billing data into the orders table (along with shipping info, etc.), but I believe the best way to do this is to store the billing data into a separate customer table. (At some point I'm going to script if customer already exists, not to create a new record...).
Do I have to add customer data into the orders table? That seems like poor database design.