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Wrox Programmer to Programmer TM

Beginning

Wrox Programmer to Programmer TM
Stephens

Database Design Solutions
Databases play a critical role in the business operations of most organizations;
they’re the central repository for critical information on products, customers,
suppliers, sales, and a host of other essential information. It’s no wonder that
the majority of all business computing involves database applications.

Beginning

This book provides readers with proven methods and tools for designing efficient,
reliable, and secure databases. Author Rod Stephens explains how a database
should be organized to ensure data integrity without sacrificing performance.
He shares procedures for designing robust, flexible, and secure databases that

provide a solid foundation for all of your database applications. The methods
and techniques in this book can be applied to any database environment,
including Oracle®, Microsoft Access®, SQL Server®, and MySQL®. You’ll learn
the basics of good database design and ultimately discover how to design a
real-world database.

What you will learn from this book
● How to identify database requirements that meet users’ needs
● Ways to build data models using a variety of modeling techniques, including
entity-relational models, user-interface models, and semantic object models
● Tips for understanding the different types of databases, including relational
Enhance Your Knowledge
databases, flat files, spreadsheets, XML and object databases
Advance Your Career
● How to refine and tune the design to improve database performance
● Techniques for understanding the relationship between good application design and database design
● Methods for designing flexible and robust databases that can adapt to business change and growth
● Ways to design for ease of maintenance and support
● How to avoid common database design mistakes

Who this book is for
This book is for anyone interested in learning to design, build, analyze, and understand databases. No previous experience with
databases or programs is required.
Wrox Beginning guides are crafted to make learning programming languages and technologies easier than you think, providing
a structured, tutorial format that will guide you through all the techniques involved.

Database Design

Solutions

With so much at stake, you’d expect most IT professionals would have a firm
understanding of good database design. But in fact most learn through a painful
process of trial and error, with predictably poor results.

Beginning

Database Design
Solutions
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Beginning

Database Design Solutions
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Beginning Database Design Solutions
978-0-470-38549-4
Beginning Database Design Solutions introduces IT professionals—both DBAs and database developers—to database design.
It explains what databases are, their goals, and why proper design is necessary to achieve those goals. It tells how to decide
what should be in a database to meet the application’s requirements. It tells how to structure the database so it gives good
performance while minimizing the chance for error.

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Beginning
Database Design Solutions
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxiii

Part I: Introduction to Databases and Database Design

1

Chapter 1: Goals of Effective Database Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Chapter 2: Database Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Chapter 3: Relational Database Fundamentals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

Part II: Database Design Process and Techniques

63

Chapter 4: Understanding User Needs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
Chapter 5: Translating User Needs into Data Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
Chapter 6: Extracting Business Rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
Chapter 7: Normalizing Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
Chapter 8: Designing Databases to Support Software Applications . . . . . . . . . . . . . . . . . . . . . 173
Chapter 9: Common Design Patterns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185
Chapter 10: Common Design Pitfalls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207

Part III: A Detailed Case Study
Chapter 11: User Needs and Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Chapter 12: Building a Data Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Chapter 13: Extracting Business Rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Chapter 14: Normalization and Refinement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Part IV: Implementing Databases (with Examples in Access
and MySQL)

225
227
245
263
273

285

Chapter 15: Microsoft Access . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287
Chapter 16: MySQL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313

Part V: Advanced Topics
Chapter 17: Introduction to SQL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Chapter 18: Building Databases with SQL Scripts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Chapter 19: Database Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Chapter 20: Database Security . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Appendix A: Exercise Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Appendix B: Sample Database Designs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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343
345
369
379
389
403
467
487
497

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Beginning

Database Design Solutions

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Beginning

Database Design Solutions
Rod Stephens

Wiley Publishing, Inc.

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Beginning Database Design Solutions
Published by
Wiley Publishing, Inc.
10475 Crosspoint Boulevard
Indianapolis, IN 46256

www.wiley.com
Copyright  2009 by Wiley Publishing, Inc., Indianapolis, Indiana
Published simultaneously in Canada
ISBN: 978-0-470-38549-4
Manufactured in the United States of America
10 9 8 7 6 5 4 3 2 1
Library of Congress Cataloging-in-Publication Data
Stephens, Rod, 1961Beginning database design solutions / Rod Stephens.
p. cm.
Includes index.
ISBN 978-0-470-38549-4 (978-0-470-38549-4)
1. Database design. 2. Databases. I. Title.
QA76.9.D26S97 2008
005.74 — dc22
2008037282
No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any
means, electronic, mechanical, photocopying, recording, scanning or otherwise, except as permitted under Sections
107 or 108 of the 1976 United States Copyright Act, without either the prior written permission of the Publisher, or
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addressed to the Legal Department, Wiley Publishing, Inc., 10475 Crosspoint Blvd., Indianapolis, IN 46256, (317)
572-3447, fax (317) 572-4355, or online at http://www.wiley.com/go/permissions.
Limit of Liability/Disclaimer of Warranty: The publisher and the author make no representations or warranties
with respect to the accuracy or completeness of the contents of this work and specifically disclaim all warranties,
including without limitation warranties of fitness for a particular purpose. No warranty may be created or extended
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available in electronic books.

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About the Author
Rod Stephens started out as a mathematician but, while studying at MIT, discovered the joys of computer
algorithms and programming and he’s been programming professionally ever since. During his career,
he has worked on a wide variety of applications in such diverse fields as telephone switching, billing,
repair dispatching, tax processing, wastewater treatment, concert ticket sales, cartography, and training
for professional football players.
Rod is a Microsoft Visual Basic Most Valuable Professional (MVP), consultant and author. He has written
18 books that have been translated into half a dozen different languages, and more than 250 magazine
articles, mostly about Visual Basic. Currently he is a regular contributor of C# and Visual Basic articles at
DevX.com (www.devx.com).
Rod’s popular VB Helper Web site www.vb-helper.com receives several million hits per month and contains thousands of pages of tips, tricks, and example code for Visual Basic programmers, as well as
example code for this book.

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Credits
Executive Editor
Robert Elliott

Production Manager
Tim Tate

Development Editor
Sydney Jones

Vice President and Executive Group Publisher
Richard Swadley

Technical Editor
Steve Hoberman

Vice President and Executive Publisher
Joseph B. Wikert

Production Editor
Angela Smith

Project Coordinator, Cover
Lynsey Stanford

Copy Editor
Kim Cofer

Proofreader
Publication Services, Inc.

Editorial Manager
Mary Beth Wakefield

Indexer
Jack Lewis

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Acknowledgments
Thanks to Bob Elliott, Sydney Jones, Steve Hoberman, and all of the others whose hard work went into
producing this book.
Special thanks to Sydney Jones for putting up with my sometimes overly generous interpretation of the
Wrox guidelines.

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Contents

Introduction

Part I:

xxiii

Introduction to Databases and Database Design

Chapter 1: Goals of Effective Database Design
Understanding the Importance of Design
Information Containers
Strengths and Weaknesses of Information Containers
Desirable Database Features
CRUD
Retrieval
Consistency
Validity
Easy Error Correction
Speed
Atomic Transactions
ACID
Persistence and Backups
Low Cost and Extensibility
Ease of Use
Portability
Security
Sharing
Ability to Perform Complex Calculations
Consequences of Good and Bad Design

Summary
Exercises

3
4
5
7
8
9
9
10
10
11
11
12
13
14
16
16
16
17
18
19
19

21
22

Chapter 2: Database Types

23

Why Bother?
Flat Files

24
24

INI Files
Windows System Registry

26
26

Relational Databases

27
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Contents
Spreadsheets
Hierarchical Databases
XML

30
31
34

XML Basics
XML Structures
XML Summary

34
37
39

Network
Object
Object-Relational
Exotic

40
42
43
44

Document-Oriented
Deductive
Dimensional
Temporal

44
44
44
45

Summary
Exercises

45
47

Chapter 3: Relational Database Fundamentals
Relational Points of View
Table, Rows, and Columns
Relations, Attributes, and Tuples
Keys
Indexes
Constraints

49
50
52
52
54
55

Basic Constraints
Check Constraints
Primary Key Constraints
Unique Constraints
Foreign Key Constraints

55
55
55
56
56

Database Operations
Summary
Exercises

Part II:

49

57
59
59

Database Design Process and Techniques

Chapter 4: Understanding User Needs
Make a Plan
Bring a List of Questions

65
66
67

Functionality
Data Needs
Data Integrity

67
67
68

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Contents
Security
Environment

68
69

Meet the Customers
Learn Who’s Who
Pick the Customers’ Brains
Walk a Mile in the User’s Shoes
Study Current Operations
Brainstorm
Look to the Future
Understand the Customers’ Reasoning
Learn What the Customers Really Need
Prioritize
Verify Your Understanding
Write the Requirements Document
Make Use Cases
Decide Feasibility
Summary
Exercises

Chapter 5: Translating User Needs into Data Models

69
70
73
73
74
75
76
76
77
78
79
80
81
85
85
86

89

What Are Data Models?
User Interface Models
Semantic Object Models

90
92
96

Classes and Objects
Cardinality
Identifiers
Putting It Together
Semantic Views
Class Types
Comments and Notes

96
97
97
97
99
100
106

Entity-Relationship Models

106

Entities, Attributes, and Identifiers
Relationships
Cardinality
Inheritance
Additional Conventions
Comments and Notes

Relational Models

107
107
108
109
112
113

113

Converting Semantic Object Models
Converting ER Diagrams

Summary
Exercises

113
116

117
118

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Contents
Chapter 6: Extracting Business Rules
What Are Business Rules?
Identifying Key Business Rules
Extracting Key Business Rules
Multi-Tier Applications
Summary
Exercises

121
121
123
128
129
133
134

Chapter 7: Normalizing Data

137

What Is Normalization?
First Normal Form (1NF)
Second Normal Form (2NF)
Third Normal Form (3NF)
Stopping at Third Normal Form
Boyce-Codd Normal Form (BCNF)
Fourth Normal Form (4NF)
Fifth Normal Form (5NF)
Domain/Key Normal Form (DKNF)
Essential Redundancy
The Best Level of Normalization
Summary
Exercises

137
138
146
150
154
154
158
162
165
167
168
169
170

Chapter 8: Designing Databases to Support Software Applications
Plan Ahead
Document Everything
Consider Multi-Tier Architecture
Convert Domains into Tables
Keep Tables Focused
Use Three Kinds of Tables
Use Naming Conventions
Allow Some Redundant Data
Don’t Squeeze in Everything
Summary
Exercises

173
173
174
175
175
176
176
178
179
180
181
182

Chapter 9: Common Design Patterns
Associations

185
185

Many-to-Many Associations
Multiple Many-to-Many Associations

186
186

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Contents
Multiple-Object Associations
Repeated Attribute Associations
Reflexive Associations

Temporal Data

188
191
193

200

Effective Dates
Deleted Objects
Deciding What to Temporalize

200
202
203

Logging and Locking

203

Audit Trails
Turnkey Records

203
204

Summary
Exercises

205
205

Chapter 10: Common Design Pitfalls
Lack of Preparation
Poor Documentation
Poor Naming Standards
Thinking Too Small
Not Planning for Change
Too Much Normalization
Insufficient Normalization
Insufficient Testing
Performance Anxiety
Mishmash Tables
Not Enforcing Constraints
Obsession with IDs
Not Defining Natural Keys
Summary
Exercises

Part III:

207
207
208
208
210
210
213
213
214
214
215
217
218
220
221
222

A Detailed Case Study

Chapter 11: User Needs and Requirements
Meet the Customers
Pick the Customers’ Brains

227
227
229

Determining What the System Should Do
Determining How the Project Should Look
Determining What Data Is Needed for the User Interface
Determining Where the Data Should Come From
Determining How the Pieces of Data Are Related
Determining Performance Needs

229
231
232
233
233
235

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Contents
Determining Security Needs
Determining Data Integrity Needs

236
236

Write Use Cases
Write the Requirements Document
Demand Feedback
Summary
Exercises

238
242
243
244
244

Chapter 12: Building a Data Model

245

Semantic Object Modeling

245

Building an Initial Semantic Object Model
Improving the Semantic Object Model

Entity-Relationship Modeling

245
248

250

Building an ER Diagram
Building a Combined ER Diagram
Improving the Entity-Relationship Diagram

Relational Modeling
Putting It All Together
Summary
Exercises

250
252
254

256
259
260
261

Chapter 13: Extracting Business Rules
Identifying Business Rules

263
263

Courses
CustomerCourses
Customers
Pets
Employees
Orders
OrderItems
InventoryItems
TimeEntries
Shifts
Persons
Phones
Vendors

264
266
267
267
267
267
268
268
268
269
269
269
269

Drawing a New Relational Model
Summary
Exercises

270
270
271

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Contents
Chapter 14: Normalization and Refinement

273

Improving Flexibility
Verifying First Normal Form
Verifying Second Normal Form

273
275
278

Pets
TimeEntries

279
280

Verifying Third Normal Form
Summary
Exercises

Part IV:

281
283
284

Implementing Databases
(with Examples in
Access and MySQL)

Chapter 15: Microsoft Access

287

Understanding Access
Getting Started
Defining Relationships
Creating Field Constraints
Creating Table Constraints
Creating Queries

287
288
293
296
298
301

Query Design View
SQL View

304
306

Summary
Exercises

308
308

Chapter 16: MySQL

313

Installing MySQL
Using MySQL Command Line Client
Executing SQL Scripts
Using MySQL Query Browser

313
314
318
319

Executing Queries
Editing Data
Creating and Modifying Databases
Using Scripts
Getting Syntax Help

320
320
321
327
329

Using MySQL Workbench

330

Loading Scripts
Creating EER Diagrams

330
331

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Contents
Editing Databases
Defining Triggers
Exporting Scripts

333
334
336

Summary
Exercises

Part V:

338
338

Advanced Topics

Chapter 17: Introduction to SQL

345

Background
Finding More Information
Standards
Basic Syntax
Command Overview
CREATE TABLE
CREATE INDEX
DROP
INSERT
SELECT

345
346
346
347
348
350
355
356
357
358

SELECT Clause
FROM Clause
WHERE Clause
GROUP BY Clause
ORDER BY Clause

358
359
362
362
363

UPDATE
DELETE
Summary
Exercises

364
365
366
366

Chapter 18: Building Databases with SQL Scripts

369

Why Bother with Scripts?
Script Categories

369
370

Database Creation Scripts
Basic Initialization Scripts
Data Initialization Scripts
Cleanup Scripts
Saving Scripts

370
370
370
371
371

Ordering SQL Commands
Summary
Exercises

371
376
377

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Contents
Chapter 19: Database Maintenance
Backups
Data Warehousing
Repairing the Database
Compacting the Database
Performance Tuning
Summary
Exercises

379
379
382
383
383
383
386
387

Chapter 20: Database Security
The Right Level of Security
Passwords

389
389
390

Single-Password Databases
Individual Passwords
Operating System Passwords
Good Passwords

Privileges
Initial Configuration and Privileges
Too Much Security
Physical Security
Summary
Exercises

Appendix A: Exercise Solutions
Chapter 1
Chapter 2
Chapter 3
Chapter 4
Chapter 5
Chapter 6
Chapter 7
Chapter 8
Chapter 9
Chapter 10
Chapter 11
Chapter 12
Chapter 13
Chapter 14
Chapter 15

390
390
391
391

392
398
398
399
400
401

403
403
408
411
413
417
424
430
434
436
440
442
446
449
451
454

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Contents
Chapter 16
Chapter 17
Chapter 18
Chapter 19
Chapter 20

454
454
457
459
460

Appendix B: Sample Database Designs
Books
DVD and Movies
Music and CDs
Documents
Customer Orders
Employee Shifts and Timesheets
Employees, Projects, and Departments
Employee Skills and Qualifications
Identical Object Rental
Distinct Object Rental
Students, Courses, and Grades
Teams
Individual Sports
Vehicle Fleets
Contacts
Passengers
Recipes

467
468
470
471
472
472
473
473
475
476
476
478
479
480
480
483
483
485

Glossary

487

Index

497

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Introduction
It has been estimated that more than 80 percent of all computer programming is database-related. This
is certainly easy to believe. After all, a database can be a powerful tool for doing exactly what computer
programs do best: store, manipulate, and display data.
Even many programs that seem at first glance to have little to do with traditional business-oriented
data use databases to make processing easier. In fact, looking back on more than 20 years of software
development experience, I’m hard pressed to think of a single non-trivial application that I’ve worked on
that didn’t use some kind of database.
Not only do databases play a role in many applications, but they also often play a critical role. If the data
is not properly stored, it may become corrupted and the program will be unable to use it meaningfully.
If the data is not properly organized, the program may be unable to find what it needs in a reasonable
amount of time.
Unless the database stores its data safely and effectively, the application will be useless no matter how
well-designed the rest of the system may be. The database is like the foundation of a building: without a
strong foundation, even the best crafted building will fail, sometimes spectacularly (the Leaning Tower
of Pisa notwithstanding).
With such a large majority of applications relying so heavily on databases, you would expect everyone involved with application development to have a solid, formal foundation in database design and
construction. Everyone including database designers, application architects, programmers, database
administrators, and project managers should ideally understand what makes a good database design.
Even an application’s key customers and users could benefit from understanding how databases work.
Sadly that is usually not the case. Many IT professionals have learned what they know about databases
through rumor, trial-and-error, and painful experience. Over the years, some develop an intuitive feel
for what makes a good database design but they may still not understand the reasons why a design is
good or bad, and they may leave behind a trail of rickety, poorly constructed programs built on shaky
database foundations.
This book provides the tools you need to design a database. It explains how to determine what should
go in a database and how a database should be organized to ensure data integrity and a reasonable
level of performance. It explains techniques for designing a database that is strong enough to store data
safely and consistently, flexible enough to allow the application to retrieve the data it needs quickly and
reliably, and adaptable enough to accommodate a realistic amount of change.

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