Sams Teach Yourself SQL in 24 Hours

By Ron Plew and Ryan Stephens

• Table of Contents
  • Copyright
  • About the Authors
  • Acknowledgments
  • Tell Us What You Think!
  • Introduction
  • Part I: A SQL Concepts Overview
  • Hour 1. Welcome to the World of SQL
  • Part II: Building Your Database
  • Hour 2. Defining Data Structures
  • Hour 3. Managing Database Objects
  • Hour 4. The Normalization Process
  • Hour 5. Manipulating Data
  • Hour 6. Managing Database Transactions
    • What Is a Transaction?
    • What Is Transactional Control?
    • Transactional Control and Database Performance
    • Summary
    • Q&A
    • Workshop
  • Part III: Getting Effective Results from Queries
  • Hour 7. Introduction to the Database Query
  • Hour 8. Using Operators to Categorize Data
  • Hour 9. Summarizing Data Results from a Query
  • Hour 10. Sorting and Grouping Data
  • Hour 11. Restructuring the Appearance of Data
  • Hour 12. Understanding Dates and Times
  • Part IV: Building Sophisticated Database Queries
  • Hour 13. Joining Tables in Queries
  • Hour 14. Using Subqueries to Define Unknown Data
  • Hour 15. Combining Multiple Queries into One
  • Part V: SQL Performance Tuning
  • Hour 16. Using Indexes to Improve Performance
  • Hour 17. Improving Database Performance
  • Part VI: Using SQL to Manage Users and Security
  • Hour 18. Managing Database Users
  • Hour 19. Managing Database Security
  • Part VII: Summarized Data Structures
  • Hour 20. Creating and Using Views and Synonyms
  • Hour 21. Working with the System Catalog
  • Part VIII: Applying SQL Fundamentals in Today's World
  • Hour 22. Advanced SQL Topics
  • Hour 23. Extending SQL to the Enterprise, the Internet, and the Intranet
  • Hour 24. Extensions to Standard SQL
  • Part IX: Appendixes
  • Appendix A. Common SQL Commands
  • Appendix B. Using MySQL for Exercises
  • Appendix C. Answers to Quizzes and Exercises
  • Appendix D. CREATE TABLE Statements for Book Examples
  • Appendix E. INSERT Statements for Data in Book Examples
  • Appendix F. Glossary
  • Appendix G. Bonus Exercises

Transactional Control and Database Performance

Poor transactional control can hurt database performance and even bring the database to a halt. Repeated poor database performance may be due to a lack of transactional control during large inserts, updates, or deletes. Not only are large batch processes, such as these demanding on the CPU and memory themselves, but temporary storage for rollback information continues to grow until either a COMMIT or ROLLBACK command is issued.

When a COMMIT is issued, rollback transactional information is written to the target table and the rollback information in temporary storage is cleared. When a ROLLBACK is issued, no changes are made to the database and the rollback information in the temporary storage is cleared. If neither a COMMIT nor ROLLBACK is issued, the temporary storage for rollback information continues to grow until there is no more space left, thus forcing the database to stop all processes until space is freed. Although space usage is ultimately controlled by the DBA, a lack of transactional control can still cause database processing to stop, sometimes forcing the DBA to take action that may consist of killing running user processes.

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