Trade Federation sells droidsand maintains the database shown in the ERD below to keep track oftheir customer purchases. A customer can make many droid purchaseswith each purchase generating an invoice. The customer’s balance isadjusted with credit purchases (increases the balance) or payments(decreases the balance), so it is always current. In addition, thelast purchase date and last payment dates are updated when thecustomer makes some business transaction with tradefederation.
Invoices contain a line for each product purchased
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