Databases Illuminated, 3rd Edition

 CHAPTER 

3

The Entity-Relationship Model

TABLE OF CONTENTS

3.1    Purpose of the E-R Model

3.2    Entities

3.3    Attributes

3.4    Keys

3.5    Relationships

3.6    Roles

3.7    Existence Dependency and Weak Entities

3.8    Sample E-R Diagrams

3.9    Rationale for Extending the E-R Model

3.10  Generalization and Specialization

3.11  Union

3.12  Sample EE-R Diagrams

3.13  Chapter Summary

Exercises

CHAPTER OBJECTIVES

In this chapter you will learn the following:

›  The meaning of enterprise schema, entity type, entity set, and entity instance

›  The meaning of attribute and domain

›  The meaning of null, multivalued, composite, and derived attributes

›  The meaning of superkey, candidate key, primary key, alternate key, and secondary key