1. Database Design Module C

2. Database Design Relationships Database Design Entities Cardinality

3. Objectives ▪ Discuss the purpose of using an ERD. ▪ Demonstrate the ability to read the details of an ERD.

4. Source Document

5. Source Data

6. What is an E-R Model or ERD? Logical representation of database

7. How are Relationships Specified?

8. How Do I Read a Relationship? ▪ A Customer may have a minimum of zero and a maximum of many Orders. ▪ An Order may belong to a minimum of one and a maximum of one Customer.

9. ERD Question

10. Feedback Question 4.According to the ERD below, what is the minimum number of participants a given observation can be associated with? A.Zero B.One C.Many

11. ERD Activity You are a very busy plumber. You do only subcontract work which means you don’t work for individual homeowners, you work for contractors. You are so successful now that you’d like to be selective about the contractors you work for. You’d like to develop a database to help you analyze which contractors give you the best work. You prefer commercial jobs to residential, and jobs that are clearly specified with few changes after the project begins. You prefer local jobs. You’ll need to keep track of basic contact information about each contractor as well as qualitative aspects of each job.

12. ERD Question A X - PK Y B Z - PK X