dolution

Defining Entities and Data Modeling— Business Rules

Given the following business rules, construct an ER diagram so each rule is captured for the database. Presume each rule is to be treated individually. Construct an ER diagram for each rule.

a. A retail sales company prepares sales orders for its customers’ purchases. A customer can make many purchases, but a sales order is written for a single customer.

b. A retail sales company orders inventory using a purchase order. An inventory item may be ordered many times, and a purchase order may be created for more than one inventory item.

c. A company that sells antique cars prepares a sales order for each car sold. The inventory for this company consists of unique automobiles, and only one of these automobiles may be listed on a sales order.

d. A grocery store identifies returning customers via a plastic card that the clerk scans at the time of each purchase. The purpose of this card is to track inventory and to maintain a database of customers and their purchases. Obviously, a customer may purchase an unlimited number of items from the grocery store. Items are unique only by a UPC code, and each UPC code may be associated with many different customers.

e. A video rental store uniquely identifies each of its inventory items so customers can rent a movie and return the movie via a drop box, and the store can identify which copy of the movie was rented and returned. A customer is allowed to rent up to six movies at a time, but a copy of a movie can only be rented by one customer at a time.