Fundamentals of Database Management Systems, Second Edition

CHAPTER 2

DATA MODELING

Before reaching database management, there is an important preliminary to cover. In order ultimately to design databases to support an organization, we must have a clear understanding of how the organization is structured and how it functions. We have to understand its components, what they do and how they relate to each other. The bottom line is that we have devise a way of recording, of diagramming, the business environment. This is the essence of data modeling.

OBJECTIVES

• Explain the concept and practical use of data modeling.
• Recognize which relationships in the business environment are unary, binary, and ternary relationships.
• Describe one-to-one, one-to-many, and many-to-many unary, binary, and ternary relationships.
• Recognize and describe intersection data.
• Model data in business environments by drawing entity-relationship diagrams that involve unary, binary, and ternary relationships.

CHAPTER OUTLINE

Introduction

Binary Relationships

• What is a Binary Relationship?
• Cardinality
• Modality
• More About Many-to-Many Relationships

Unary Relationships

• One-to-One Unary Relationship
• One-to-Many Unary Relationship
• Many-to-Many Unary Relationship

Ternary Relationships

Example: The General Hardware Company

Example: Good Reading Book Stores

Example: World Music Association

Example: Lucky Rent-A-Car

Summary

INTRODUCTION

The diagramming technique we will use is called the entity-relationship or E-R Model. It is well named, as it diagrams entities (together with ...