Entity Relationship Diagrams (ERDs)

1. Entity Relationship Diagrams (ERDs)

2. Entity Relationship Diagram (ERD) • documentation technique to represent relationship between entitiesin system. • Think of entities as “nouns” – nouns on which a company would want to track information. A few examples: • Vehicles • Accounts Receivable • Customers • Vendors

3. Entity Relationship Diagram (ERD) • Think of the relationship as a “verb” • The verb connects (relates) one entity to another. A few examples: • Receive • Assign • Prepare • Send

4. Depends on business rules !! Cardinality between entities • represents the numerical mapping between entities: • one-to-one • one-to-many • many-to-many

5. Cardinalities Entity Relationship Entity 1 1 Sales- person Car is assigned Customer Company A

6. Cardinalities Entity Relationship Entity 1 M Sales- person Car is assigned Company B Customer

7. Cardinalities Entity Relationship Entity 1 M places Order Customer This cardinality is probably true for most businesses.

8. Cardinalities Entity Relationship Entity M M Vendor Inventory supplies This cardinality would depend on the business.

9. ERD – Expenditure Cycle

10. Describe the business rules represented by the cardinalities in the ERD. VENDOR 1 1 M M P.O. M INVENTORY M 1 M M REC. RPT. 1

11. Add 3 attributes for each entity. VENDOR 1 1 M M P.O. M INVENTORY M 1 M M REC. RPT. 1

12. 3 attributes for each entity. VENDOR 1 M 1 M P.O. M INVENTORY M 1 M M REC. RPT. 1

13. Modify the ERD, based on the following information: 1 The Vendor sends an invoice for each shipment.The invoice is matched tothe RR; a Cash Disbursement (CD) is prepared for each invoice. VENDOR 1 M M M P.O. M INVENTORY 1 M M 1 REC. RPT. 13

14. VENDOR 1 1 M M P.O. M INVENTORY M 1 M M REC. RPT. 1

15. Add 3 attributes for each new entity. VENDOR 1 1 M M P.O. M INVENTORY M 1 M M REC. RPT. 1

16. The End