067232976x_ch15.qxd

4/1/08

4:03 PM

Page 1

15

Understanding the Database Design Process
In this chapter, you’ll learn the thought processes behind designing a relational database. After this theory-focused chapter, you’ll jump headlong into learning the basic MySQL commands in preparation for integrating MySQL in your own applications. Topics covered in this chapter are

. Some advantages to good database design . Three types of table relationships . How to normalize your database . How to implement a good database design process

The Importance of Good Database Design
A good database design is crucial for a high-performance application, just as an aerodynamic body is important to a race car. If the car doesn’t have smooth lines, it will produce drag and go slower. Without optimized relationships, your database won’t perform as efficiently as possible. Thinking about relationships and database efficiency is part of normalization. Beyond the issue of performance is the issue of maintenance—your database should be easy to maintain. This includes storing only a limited amount (if any) of repetitive data. If you have a lot of repetitive data and one instance of that data undergoes a change (such as a name change), that change has to be made for all occurrences of the data. To eliminate duplication and enhance your ability to maintain the data, you might create a table of possible values and use a key to refer to the value. That way, if the value changes names, the change occurs only once—in the master table. The reference remains the same throughout other tables.

067232976x_ch15.qxd

4/1/08

4:03 PM

Page 2

2

15: Understanding the Database Design Process

By the Way

Normalization refers to the process of structuring data in order to minimize duplication and inconsistencies.

For example, suppose that you are responsible for