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CHAPTER2

DATA MODELS AND RELATIONAL

DATABASES

INTRODUCTION

The database development process begins with enterprise modeling to set the range and
general contents of organizational databases as presented in Chapter 1. The example of an
enterprise model is reproduced in Figure 2-1 for a review.
Then, in the conceptual data modeling stage, the requirements of overall entities
are analyzed based on transaction cycles. For example, Figure 2-2 is a conceptual data
model for Cherokee's revenue and expenditure cycles as discussed in Chapter 1.
This chapter concerns logical database design. Logical database design is the process
of transforming the conceptual data model into a logical data model. The logical data mod-
els used in this chapter are relational data models. Most information systems today are based
on relational databases, the most popular type of databases used for transaction processing.
The purpose of this chapter is to expand on our discussion in Chapter 1 using business-
process-based data models to design a relational database. This chapter presents important
concepts and definitions of relational databases. In addition, the processes of normaliza-
tion that determine whether a table is well designed and eliminate possible anomalies in
the table are also discussed. After completing this chapter, you should be able, based on a
data model, to accomplish the following:

• Identify primary and foreign keys for each entity and relationship in the data model

• Create tables that are linked properly with foreign keys or through relationship table(s)
• Examine whether a table design has any anomalies
• Normalize a table to third normal form

RELATIONAL DATABASES

Basic Concepts and Definitions

4
A database is an organized collection of logically related data that are stored in tables
(or files). There are three main constructs of the structure of a relational database. The pri-
mary construct is called a relation or a table, that is a storage structure with rows and

4Data are facts, text, and images that can be recorded and stored on computer media, such as customer names,
logos, and addresses. Information is data that has been processed and organized in such a way that it can
increase the knowledge of decision makers, such as a report with the due date and accounts receivable balance
of each customer.