Database Reference
In-Depth Information
5
DATABASE DESIGN 1:
NORMALIZATION
CHAPTER
LEARNING OBJECTIVES
Discuss functional dependence and primary keys
Define first normal form, second normal form, third normal form, and fourth normal form
Describe the problems associated with tables (relations) that are not in first normal form, sec-
ond normal form, or third normal form, along with the mechanism for converting to all three
Discuss the problems associated with incorrect conversions to third normal form
Describe the problems associated with tables (relations) that are not in fourth normal form and
describe the mechanism for converting to fourth normal form
Understand how normalization is used in the database design process
INTRODUCTION
You have examined the basic relational model, its structure, and the various ways of manipulating data within a relational
database. In this chapter, you will learn about the normalization process and its underlying concepts and features. The
nor-
malization process
enables you to identify the existence of potential problems, called
update anomalies
, in the design of
a relational database. This process also supplies methods for correcting these problems.
To correct update anomalies in a database, you must convert tables to various types of
. A table in a
particular normal form possesses a certain desirable collection of properties. The most common normal forms are first nor-
mal form (1NF), second normal form (2NF), third normal form (3NF), and fourth normal form (4NF). Normalization is a pro-
gression in which a table that is in first normal form is better (freer from problems) than a table that is not in first normal
form, a table that is in second normal form is better than one that is in first normal form, and so on. The goal of normaliza-
tion is to take a table or collection of tables and produce a new collection of tables that represents the same information but
that is free of update anomalies.
In this chapter, you will learn about two crucial concepts that are fundamental to understanding the normalization pro-
cess: functional dependence and keys. You will also learn about first, second, third, and fourth normal form.
Many of the examples in this chapter use data from the Premiere Products database, which is shown in Figure 5-1.
normal forms
