A New Database
We are about to build a new database for order processing. A greatly simplified version of the database will look as shown in Figure 1.
Figure 1 Database schema for a simplified database for order processing.
As you can see in Figure 1, ordermaster.id and orderdetail.id are primary keys. There are also several foreign keys: namely, ordermaster.customer_id, orderdetail.ordermaster_id, and orderdetail.product_id.
In this simplified model, I skipped adding the product and the customer tables, so ordermaster.customer_id and orderdetail.product_id aren't implemented as physical foreign keys.
We should take into consideration all of these primary and foreign keys when deciding on the datatype to use.