Physical Database Design

342 CHAPTER 15 Denormalization

15.2 Common Types of Denormalization

Denormalization is often used to suggest alternative logical structures (schemas) during

physical design and thus provides the designers with other feasible solutions to choose

from. More efficient databases are the likely outcome of evaluating alternative struc-

tures. This process is referred to as denormalization because the schema transformation

can cause the degree of normalization in the resulting table to be less than the degree of

at least one of the original tables.

The two most common types of denormalization are two entities in a one-to-one

relationship and two entities in a one-to-many relationship.

15.2.1 Two Entities in a One-to-One Relationship

The tables for these entities ...