What are the transaction processing techniques for learning MySQL?

What are the transaction processing techniques for learning MySQL?

Introduction:
Transaction is a very important concept in database management system. It provides a mechanism to ensure data integrity and consistency. In MySQL, a transaction is the execution unit of a set of SQL statements, which can ensure that all SQL statements in this set of statements are either successfully executed or rolled back if all execution fails. This article will introduce the transaction processing skills of learning MySQL and give corresponding code examples.

1. Opening a transaction:
   In MySQL, you can use BEGIN, START TRANSACTION or SET AUTOCOMMIT=0 to open a transaction. Among them, BEGIN and START TRANSACTION are equivalent. They will set the autocommit mode to 0, indicating that the automatic commit mode is turned off, that is, the transaction needs to be submitted manually. SET AUTOCOMMIT=0 only turns off the automatic commit mode, and the transaction is not actually started.

Code example:

BEGIN;
-- 或
START TRANSACTION;
-- 或
SET AUTOCOMMIT=0;

2. Commit transaction:
   In MySQL, you can use the COMMIT statement to submit a transaction. When all SQL statements are executed successfully, we can persist the data to the database through COMMIT.

Code example:

COMMIT;

3. Rollback transaction:
   In MySQL, you can use the ROLLBACK statement to rollback a transaction. When an error occurs during execution, or previous operations need to be undone, ROLLBACK can be used to roll back the transaction to its previous state.

Code example:

ROLLBACK;

4. Set save point:
   In MySQL, you can use the SAVEPOINT statement to set a save point, that is, at a certain point during transaction execution Create a mark point at a time point to facilitate rolling back to that time point in subsequent operations. Use the ROLLBACK TO statement to roll back to a savepoint.

Code example:

SAVEPOINT savepoint1;
-- 执行一些SQL操作
ROLLBACK TO savepoint1;

5. Set transaction isolation level:
   In MySQL, you can control data visibility during concurrent operations by setting the isolation level of a transaction and concurrent performance. MySQL supports four isolation levels: READ UNCOMMITTED, READ COMMITTED, REPEATABLE READ and SERIALIZABLE. You can use the following statement to set the transaction isolation level:

Code example:

SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;
-- 或
SET TRANSACTION ISOLATION LEVEL READ COMMITTED;
-- 或
SET TRANSACTION ISOLATION LEVEL REPEATABLE READ;
-- 或
SET TRANSACTION ISOLATION LEVEL SERIALIZABLE;

6. Use of locks:
   In MySQL, concurrent access can be controlled through the lock mechanism and modify data. Locks can be divided into shared locks and exclusive locks. A shared lock allows other transactions to acquire shared locks and can hold multiple shared locks at the same time; an exclusive lock cannot acquire any locks when held by one transaction.

Code sample:

-- 获取共享锁
SELECT * FROM table_name WHERE column_name = 'value' FOR SHARE;
-- 获取排他锁
SELECT * FROM table_name WHERE column_name = 'value' FOR UPDATE;

7. Exception handling:
   During transaction processing, various exceptions may be encountered. In order to ensure the integrity and stability of transactions, we need exception handling. In MySQL, exceptions can be defined using the DECLARE statement and caught and handled using the HANDLER statement.

Code example:

DECLARE my_error CONDITION FOR SQLSTATE '45000';
DECLARE CONTINUE HANDLER FOR my_error
BEGIN
    -- 处理异常情况
END;

Conclusion:
By learning MySQL transaction processing skills, we can effectively ensure the integrity and consistency of data, and improve the efficiency of database processing Concurrency performance. It should be noted that transaction processing needs to be used with caution to avoid data inconsistency or deadlock.

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