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MySQL Tutorial - Read Consistency Support in MySQL

By: FYIcenter.com

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How Does MySQL Handle Read Consistency?

Read consistency is a concept that describes how consistent the output will be on two subsequent read operations. A read operation is usually a stand alone SELECT statement or a SELECT subquery in a parent statement.

A database server can support up to 3 levels of read consistency:

• No Read Consistency - Two subsequent read operations will get no consistent output, if other sessions are making changes to the database.
• Statement-Level Read Consistency - Two subsequent read operations will get consistent output, if they are used as subqueries within a single SQL statement.
• Transaction-Level Read Consistency - Two subsequent read operations will get consistent output, if they are used as subqueries or SELECT statements within a single transaction.

By default, MySQL server offers the highest level, Transaction-Level Read Consistency, on tables with transaction-safe storage engines, like InnoDB.

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1. What Is a Transaction?
2. How To Start a New Transaction?
3. How To End the Current Transaction?
4. How To Create a Table for Transaction Testing?
5. How To Switch between Autocommit-On and Autocommit-Off Modes?
6. How To Find Out the Current Transaction Mode?
7. How To Start a New Transaction Explicitly?
8. How To Commit the Current Transaction?
9. How To Rollback the Current Transaction?
10. What Happens to the Current Transaction If a START TRANSACTION Is Executed?
11. What Happens to the Current Transaction If a DDL Statement Is Executed?
12. What Happens to the Current Transaction If the Session Is Ended?
13. What Happens to the Current Transaction If the Session Is Killed?
14. How Does MySQL Handle Read Consistency?
15. What Are Transaction Isolation Levels?
16. How To View and Change the Current Transaction Isolation Level?
17. What Is a Data Lock?
18. How To Experiment Data Locks?
19. How Long a Transaction Will Wait for a Data Lock?
20. What Happens to Your Transactions When ERROR 1205 Occurred?
21. What Is a Dead Lock?
22. How To Experiment Dead Locks?
23. What Happens to Your Transactions When ERROR 1213 Occurred?
24. What Are Impacts on Applications from Locks, Timeouts, and DeadLocks?