Sams Teach Yourself SQL in 24 Hours
- 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
- 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
What Is a Transaction?
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A transaction is a unit of work that is performed against a database. Transactions are units or sequences of work accomplished in a logical order, whether in a manual fashion by a user or automatically by some sort of a database program. In a relational database using SQL, transactions are accomplished using the DML commands that were discussed during Hour 5, "Manipulating Data" (INSERT, UPDATE, and DELETE). A transaction is the propagation of one or more changes to the database. For instance, you are performing a transaction if you performed an UPDATE statement on a table to change an individual's name. |
A transaction can either be one DML statement or a group of statements. When managing transactions, each designated transaction (group of DML statements) must be successful as one entity or none of them will be successful.
The following list describes the nature of transactions:
- All transactions have a beginning and an end.
- A transaction can be saved or undone.
- If a transaction fails in the middle, no part of the transaction can be saved to the database.
What Is Transactional Control? | Next Section
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