本书展示了如何在不改变语义的情况下，对表结构、数据、存储过程及触发器等略作改动，就可以给数据库设计带来实质上的飞跃。

　　这是一本内容全面的参考、指南书，全面介绍了数据库重构涉及的每个基本观念，运用完整的实例，带领读者学习从重构简单的孤立数据库应用程序到重构复杂的多应用程序环境的全过程，并讲述了数据库重整的五大主要类别。读者将学会如何运用重构改善数据库结构、数据质量和参照完整性，如何同时对结构和方法进行重整。本书提供了用Oracle和Java建立的多种实例，并可以方便地转换成C#、C++、VB.NET等其他语言或DB2、SQL Server、MySQL、Sybase等其他数据库。

　　运用本书的技术和实例，读者可以减少浪费和重复工作，降低风险和成本，建立能够顺利发展以适应未来需求的数据库系统。

重构技术已经在领域广泛的开发项目中证明了自身的价值——帮助软件专业人士改善系统的设计、可维护性、可扩展性和性能。本书首次披露了为数据库系统专门设计的强大重构技术。　　本书展示了如何在不改变语义的情况下，对表结构、数据、存储过程及触发器等略作改动，就可以给数据库设计带来实质上的飞跃。　　这是一本内容全面的参考、指南书，全面介绍了数据库重构涉及的每个基本观念，运用完整的实例，带领读者学习从重构简单的孤立数据库应用程序到重构复杂的多应用程序环境的全过程，并讲述了数据库重整的五大主要类别。读者将学会如何运用重构改善数据库结构、数据质量和参照完整性，如何同时对结构和方法进行重整。本书提供了用Oracle和Java建立的多种实例，并可以方便地转换成C#、C++、VB.NET等其他语言或DB2、SQL Server、MySQL、Sybase等其他数据库。　　运用本书的技术和实例，读者可以减少浪费和重复工作，降低风险和成本，建立能够顺利发展以适应未来需求的数据库系统。

Chapter 1: Evolutionary Database Development　1

1.1　Database Refactoring　3

1.2　Evolutionary Data Modeling　4

1.3　Database Regression Testing　6

1.4　Configuration Management of Database Artifacts　9

1.5　Developer Sandboxes　10

1.6　Impediments to Evolutionary Database Development Techniques　11

1.7　What You Have Learned　12

Chapter 2: Database Refactoring　13

2.1　Code Refactoring　13

2.2　Database Refactoring　14

2.2.1　Single-Application Database Environments　15

2.2.2　Multi-Application Database Environments　18

2.2.3　Maintaining Semantics　20

2.3　Categories of Database Refactorings　22

2.4　Database Smells　22

2.5　How Database Refactoring Fits In　25

2.6　Making It Easier to Refactor Your Database Schema　27

2.7　What You Have Learned　28

Chapter 3: The Process of Database Refactoring　29

3.1　Verify That a Database Refactoring Is Appropriate　32

3.2　Choose the Most Appropriate Database Refactoring　33

3.3　Deprecate the Original Database Schema　34

3.4　Test Before, During, and After　37

3.4.1　Testing Your Database Schema　37

3.4.2　Validating Your Data Migration　38

3.4.3　Testing Your External Access Programs　40

3.5　Modify the Database Schema　40

3.6　Migrate the Source Data　43

3.7　Refactor External Access Program(s)　44

3.8　Run Your Regression Tests　45

3.9　Version Control Your Work　45

3.10　Announce the Refactoring　46

3.11　What You Have Learned　47

Chapter 4: Deploying into Production　49

4.1　Effectively Deploying Between Sandboxes　50

4.2　Applying Bundles of Database Refactorings　51

4.3　Scheduling Deployment Windows　53

4.4　Deploying Your System　54

4.5　Removing Deprecated Schema　56

4.6　What You Have Learned　56

Chapter 5: Database Refactoring Strategies　59

5.1　Smaller Changes Are Easier to Apply　60

5.2　Uniquely Identify Individual Refactorings　60

5.3　Implement a Large Change by Many Small Ones　62

5.4　Have a Database Configuration Table　63

5.5　Prefer Triggers over Views or Batch Synchronization　63

5.6　Choose a Sufficient Transition Period　65

5.7　Simplify Your Database Change Control Board (CCB) Strategy　65

5.8　Simplify Negotiations with Other Teams　65

5.9　Encapsulate Database Access　66

5.10　Be Able to Easily Set Up a Database Environment　66

5.11　Do Not Duplicate SQL　67

5.12　Put Database Assets Under Change Control　67

5.13　Beware of Politics　68

5.14　What You Have Learned　68 Online Resources　68

Chapter 6: Structural Refactorings　69

　Common Issues When Implementing Structural Refactorings　70

　Drop Column　72

　Drop Table　77

　Drop View　79

　Introduce Calculated Column　81

　Introduce Surrogate Key　85

　Merge Columns　92

　Merge Tables　96

　Move Column　103

　Rename Column　109

　Rename Table　113

　Rename View　117

　Replace LOB With Table　120

　Replace Column　126

　Replace One-To-Many With Associative Table　130

　Replace Surrogate Key With Natural Key　135

　Split Column　140

　Split Table　145

Chapter 7: Data Quality Refactorings　151

　Common Issues When Implementing Data Quality Refactorings　152

　Add Lookup Table　153

　Apply Standard Codes　157

　Apply Standard Type　162

　Consolidate Key Strategy　168

　Drop Column Constraint　172

　Drop Default Value　174

　Drop Non-Nullable　177

　Introduce Column Constraint　180

　Introduce Common Format　183

　Introduce Default Value　186

　Make Column Non-Nullable　189

　Move Data　192

　Replace Type Code With Property Flags　196

Chapter 8: Referential Integrity Refactorings　203

　Add Foreign Key Constraint　204

　Add Trigger For Calculated Column　209

　Drop Foreign Key Constraint　213

　Introduce Cascading Delete　215

　Introduce Hard Delete　219

　Introduce Soft Delete　222

　Introduce Trigger For History　227

Chapter 9: Architectural Refactorings　231

　Add CRUD Methods　232

　Add Mirror Table　236

　Add Read Method　240

　Encapsulate Table With View　243

　Introduce Calculation Method　245

　Introduce Index　248

　Introduce Read-Only Table　251

　Migrate Method From Database　257

　Migrate Method To Database　261

　Replace Method(s) With View　265

　Replace View With Method(s)　268

　Use Official Data Source　271

Chapter 10: Method Refactorings　277

10.1　Interface Changing Refactorings　277

10.1.1　Add Parameter　278

10.1.2　Parameterize Method　278

10.1.3　Remove Parameter　279

10.1.4　Rename Method　279

10.1.5　Reorder Parameters　281

10.1.6　Replace Parameter with Explicit Methods　282

10.2　Internal Refactorings　283

10.2.1　Consolidate Conditional Expression　283

10.2.2　Decompose Conditional　284

10.2.3　Extract Method　285

10.2.4　Introduce Variable　287

10.2.5　Remove Control Flag　289

10.2.6　Remove Middle Man　289

10.2.7　Rename Parameter　290

10.2.8　Replace Literal with Table Lookup　290

10.2.9　Replace Nested Conditional with Guard Clauses　292

10.2.10　Split Temporary Variable　292

10.2.11　Substitute Algorithm　293

Chapter 11: Transformations　295

　Insert Data　296

　Introduce New Column　301

　Introduce New Table　304

　Introduce View　306

　Update Data　310

Appendix: The UML Data Modeling Notation　315

Glossary　321

References and Recommended Reading　327

Index　331