CMPS 160: Databases

Introduction

By now you should have a pretty good idea what a database is and how it works. However, we have not really discussed yet how one would turn a problem into a database solution. That is the topic of this module. A data model is a representation of reality that captures the essential elements of a problem and models relationships between entities. Therefore, a data model is also known as an Entity-Relationship (E-R) data model. There are different types of relationships between entities that can be modeled, including one-to-one, one-to-many, and many-to-many relationships. We also consider identifying and non-identifying relationships.

Module Objectives

• Learn the basic stages of database development
• Understand the purpose and role of a data model
• Know the principal components of the E-R data model
• Understand how to interpret traditional E-R diagrams
• Understand how to interpret the Information Engineering (IE) model’s Crow’s Foot E-R diagrams
• Learn to construct E-R diagrams
• Know how to represent 1:1, 1:N, N:M, and binary relationships with the E-R model
• Understand two types of weak entities and know how to use them
• Understand nonidentifying and identifying relationships and know how to use them
• Know how to represent subtype entities with the E-R model
• Learn how to create an E-R diagram from source documents

Learning Resources

• Module 6 Readings: Chapter 4 (first half)
• Module 6 Slides: Chapter 4 (first half)

Learning Activities

• Module 6 Quiz: Chapter 4

Strong and Weak Entities

Here is an overview of the way the book deals with strong and weak entities:

Further Study

It is highly recommended to work through the exercises at the end of the chapter, specifically:

• 4.15 – 4.20
• Washington State Patrol Case Questions