One aspect of sound table design is to have a field (or group of fields) with a value unique to each row in the table. The fields that have the unique value are called the primary key field(s). Because each row’s primary key field (or fields) contains a unique value, Access can distinguish each row from all of the other rows in the table. Why is that important? Consider what would happen if a store used your phone number to identify you when you called in to place an order. If you change phone numbers and the next person assigned your phone number calls in before you do, the store replaces your information with the new caller’s, potentially wiping out any record you had of doing business with the store.