Database Design for Mere Mortals

Michael J. Hernandez, a relational database developer with more than twenty years of experience, was a program manager and product manager for Microsoft’s Visual Studio group. He has been a premier instructor with organizations such as AppDev Training Co., Focal Point, Inc., and Deep Training, and was a top-rated speaker at technical conferences across the United States, Europe, and South America. With John L. Viescas, he coauthored SQL Queries for Mere Mortals®, Second Edition (Addison-Wesley, 2008).

Foreword xxi Preface xxv

Acknowledgments xxvii

Introduction xxix

 

Part I: Relational Database Design 1

 

Chapter 1: The Relational Database 3

Topics Covered in This Chapter 3

Types of Databases 4

Early Database Models 5

The Hierarchical Database Model 5

The Network Database Model 9

The Relational Database Model 12

Retrieving Data 15

Advantages of a Relational Database 16

Relational Database Management Systems 18

Beyond the Relational Model 19

What the Future Holds 21

A Final Note 22

Summary 22

Review Questions 24

 

Chapter 2: Design Objectives 25

Topics Covered in This Chapter 25

Why Should You Be Concerned with Database Design? 25

The Importance of Theory 27

The Advantage of Learning a Good Design Methodology 29

Objectives of Good Design 30

Benefits of Good Design 31

Database Design Methods 32

Traditional Design Methods 32

The Design Method Presented in This Book 34

Normalization 35

Summary 38

Review Questions 39

 

Chapter 3: Terminology 41

Topics Covered in This Chapter 41

Why This Terminology Is Important 41

Value-Related Terms 43

Data 43

Information 43

Null 45

The Value of Nulls 46

The Problem with Nulls 47

Structure-Related Terms 49

Table 49

Field 52

Record 53

View 54

Keys 56

Index 58

Relationship-Related Terms 59

Relationships 59

Types of Relationships 60

Types of Participation 65

Degree of Participation 66

Integrity-Related Terms 67

Field Specification 67

Data Integrity 68

Summary 69

Review Questions 70

 

Part II: The Design Process 73

 

Chapter 4: Conceptual Overview 75

Topics Covered in This Chapter 75

The Importance of Completing the Design Process 76

Defining a Mission Statement and Mission Objectives 77

Analyzing the Current Database 78

Creating the Data Structures 80

Determining and Establishing Table Relationships 81

Determining and Defining Business Rules 81

Determining and Defining Views 83

Reviewing Data Integrity 83

Summary 84

Review Questions 86

 

Chapter 5: Starting the Process 89

Topics Covered in This Chapter 89

Conducting Interviews 89

Participant Guidelines 91

Interviewer Guidelines (These Are for You) 93

The Case Study: Mike’s Bikes 98

Defining the Mission Statement 100

The Well-Written Mission Statement 100

Composing a Mission Statement 102

Defining the Mission Objectives 105

Well-Written Mission Objectives 106

Composing Mission Objectives 108

Summary 112

Review Questions 113

 

Chapter 6: Analyzing the Current Database 115

Topics Covered in This Chapter 115

Getting to Know the Current Database 115

Paper-Based Databases 118

Legacy Databases 119

Conducting the Analysis 121

Looking at How Data Is Collected 121

Looking at How Information Is Presented 125

Conducting Interviews 129

Basic Interview Techniques 130

Before You Begin the Interview Process . . . 137

Interviewing Users 137

Reviewing Data Type and Usage 138

Reviewing the Samples 140

Reviewing Information Requirements 144

Interviewing Management 152

Reviewing Current Information Requirements 153

Reviewing Additional Information Requirements 154

Reviewing Future Information Requirements 155

Reviewing Overall Information Requirements 155

Compiling a Complete List of Fields 157

The Preliminary Field List 157

The Calculated Field List 164

Reviewing Both Lists with Users and Management 165

Case Study 166

Summary 171

Review Questions 172

 

Chapter 7: Establishing Table Structures 175

Topics Covered in This Chapter 175

Defining the Preliminary Table List 176

Identifying Implied Subjects 176

Using the List of Subjects 178

Using the Mission Objectives 182

Defining the Final Table List 184

Refining the Table Names 186

Indicating the Table Types 192

Composing the Table Descriptions 192

Associating Fields with Each Table 199

Refining the Fields 202

Improving the Field Names 202

Using an Ideal Field to Resolve Anomalies 206

Resolving Multipart Fields 210

Resolving Multivalued Fields 212

Refining the Table Structures 219

A Word about Redundant Data and Duplicate Fields 219

Using an Ideal Table to Refine Table Structures 220

Establishing Subset Tables 228

Case Study 233

Summary 240

Review Questions 242

 

Chapter 8: Keys 243

Topics Covered in This Chapter 243

Why Keys Are Important 244

Establishing Keys for Each Table 244

Candidate Keys 245

Primary Keys 253

Alternate Keys 260

Non-keys 261

Table-Level Integrity 261

Reviewing the Initial Table Structures 261

Case Study 263

Summary 269

Review Questions 270

 

Chapter 9: Field Specifications 273

Topics Covered in This Chapter 273

Why Field Specifications Are Important 274

Field-Level Integrity 275

Anatomy of a Field Specification 277

General Elements 277

Physical Elements 285

Logical Elements 292

Using Unique, Generic, and Replica Field Specifications 300

Defining Field Specifications for Each Field in the Database 306

Case Study 308

Summary 310

Review Questions 311

 

Chapter 10: Table Relationships 313

Topics Covered in This Chapter 313

Why Relationships Are Important 314

Types of Relationships 315

One-to-One Relationships 316

One-to-Many Relationships 319

Many-to-Many Relationships 321

Self-Referencing Relationships 329

Identifying Existing Relationships 333

Establishing Each Relationship 344

One-to-One and One-to-Many Relationships 345

The Many-to-Many Relationship 352

Self-Referencing Relationships 358

Reviewing the Structure of Each Table 364

Refining All Foreign Keys 365

Elements of a Foreign Key 365

Establishing Relationship Characteristics 372

Defining a Deletion Rule for Each Relationship 372

Identifying the Type of Participation for Each Table 377

Identifying the Degree of Participation for Each Table 380

Verifying Table Relationships with Users and Management 383

A Final Note 383

Relationship-Level Integrity 384

Case Study 384

Summary 389

Review Questions 391

 

Chapter 11: Business Rules 393

Topics Covered in This Chapter 393

What Are Business Rules? 393

Types of Business Rules 397

Categories of Business Rules 399

Field-Specific Business Rules 399

Relationship-Specific Business Rules 401

Defining and Establishing Business Rules 402

Working with Users and Management 402

Defining and Establishing Field-Specific Business Rules 403

Defining and Establishing Relationship-Specific Business Rules 412

Validation Tables 417

What Are Validation Tables? 419

Using Validation Tables to Support Business Rules 420

Reviewing the Business Rule Specifications Sheets 425

Case Study 426

Summary 431

Review Questions 434

 

Chapter 12: Views 435

Topics Covered in This Chapter 435

What Are Views? 435

Anatomy of a View 437

Data View 437

Aggregate View 442

Validation View 446

Determining and Defining Views 448

Working with Users and Management 449

Defining Views 450

Reviewing the Documentation for Each View 458

Case Study 460

Summary 465

Review Questions 466

 

Chapter 13: Reviewing Data Integrity 469

Topics Covered in This Chapter 469

Why You Should Review Data Integrity 470

Reviewing and Refining Data Integrity 470

Table-Level Integrity 471

Field-Level Integrity 471

Relationship-Level Integrity 472

Business Rules 472

Views 473

Assembling the Database Documentation 473

Done at Last! 475

Case Study—Wrap-Up 475

Summary 476

 

Part III: Other Database Design Issues 477

 

Chapter 14: Bad Design—What Not to Do 479

Topics Covered in This Chapter 479

Flat-File Design 480

Spreadsheet Design 481

Dealing with the Spreadsheet View Mind-set 483

Database Design Based on the Database Software 485

A Final Thought 486

Summary 487

 

Chapter 15: Bending or Breaking the Rules 489

Topics Covered in This Chapter 489

When May You Bend or Break the Rules? 489

Designing an Analytical Database 489

Improving Processing Performance 490

Documenting Your Actions 493

Summary 495

 

In Closing 497

 

Part IV: Appendixes 499

 

Appendix A: Answers to Review Questions 501

Chapter 1 501

Chapter 2 502

Chapter 3 504

Chapter 4 505

Chapter 5 506

Chapter 6 508

Chapter 7 510

Chapter 8 513

Chapter 9 516

Chapter 10 518

Chapter 11 520

Chapter 12 521

 

Appendix B: Diagram of the Database Design Process 525

 

Appendix C: Design Guidelines 543

Defining and Establishing Field-Specific Business Rules 543

Defining and Establishing Relationship-Specific Business Rules 543

Elements of a Candidate Key 544

Elements of a Foreign Key 544

Elements of a Primary Key 545

Rules for Establishing a Primary Key 545

Elements of the Ideal Field 545

Elements of the Ideal Table 546

Field-Level Integrity 546

Guidelines for Composing a Field Description 547

Guidelines for Composing a Table Description 547

Guidelines for Creating Field Names 548

Guidelines for Creating Table Names 548

Identifying Relationships 549

Identifying View Requirements 549

Interview Guidelines 550

Participant Guidelines 550

Interviewer Guidelines 550

Mission Statements 551

Mission Objectives 551

Relationship-Level Integrity 551

Resolving a Multivalued Field 552

Table-Level Integrity 552

 

Appendix D: Documentation Forms 553

 

Appendix E: Database Design Diagram Symbols 557

 

Appendix F: Sample Designs 559

 

Appendix G: On Normalization 567

Please Note . . . 568

A Brief Recap 569

How Normalization Is Integrated into My Design Methodology 572

Logical Design versus Physical Design and Implementation 575

 

Appendix H: Recommended Reading 577

 

Glossary 579

References 595

Index 597