This lab will introduce you to the processes involved in defining one of the key components of a data model; the relationship diagram (RD). In this lab, you will draw a relationship diagram for two of the steps shown. Keep in mind when you are trying to decide which side of the relationship should be the “one” side and which should be the “many” that you must first decide which side has the primary key, or unique identifier. Once you have decided the primary key of the relationship, you have identified the “one” side of the relationship. Note that for an RD, the foreign key “many” side of the relationship points to the primary key “one” side. The “one” side should have the arrowhead point of the connecting line. This is different than an entity/relationship diagram (ERD) that we will draw next week, where the “many” side has crow’s feet.
This will familiarize you with how to set up MS Visio to draw database diagrams. Steps 1 – 3 below use the Customer, Order, and Employee tables of a simplified Order Entry database. The Customer table records clients who have placed orders. The Order table contains the basic facts about customer orders. The Employee table contains facts about employees who take orders. The primary keys of the tables are CustNo for Customer, EmpNo for Employee, and OrdNo for Order.
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