In-depth explanation of how to use MySQL transactions, including ROLLBACK and COMMIT functionalities.

2 years ago
Liam
3 minutes

MySQL transactions are a collection of SQL statements that must be executed atomically, either all successfully executed or all rolled back. To control and protect data integrity in the database, MySQL provides ROLLBACK and COMMIT statements.

  1. The ROLLBACK statement is used to undo all the changes made in the current transaction. When an SQL statement encounters an error or an exception occurs during transaction processing, the ROLLBACK statement can be used to revert the previous changes and restore the database to its state before the transaction began.

Instructions for use:

ROLLBACK;
  1. COMMIT statement:
    The COMMIT statement is used to save all changes made in the current transaction to the database. When all SQL statements in the transaction are executed successfully without any exceptions, the COMMIT statement can be used to submit the changes and permanently save them to the database.

Directions for use:

COMMIT;
  1. The use of transactions:
    The steps for using transactions are as follows:
  1. Start a transaction: initiate a new transaction using the BEGIN or START TRANSACTION statement.
  2. Execute SQL statements: Perform the necessary SQL operations, such as inserting, updating, and deleting, within a transaction.
  3. Decision: Based on the execution result of the SQL statement, determine whether to continue or rollback the transaction.
  4. Submit or rollback: If all SQL statements are successfully executed, you can use the COMMIT statement to submit the changes; if there is an error or exception, you can use the ROLLBACK statement to rollback the transaction.

Example of use:

BEGIN;
INSERT INTO table1 (column1, column2) VALUES (value1, value2);
UPDATE table2 SET column1 = value1 WHERE condition;
DELETE FROM table3 WHERE condition;
IF (condition) THEN
    COMMIT;
ELSE
    ROLLBACK;
END IF;

Please take note:

  1. Transactions are only effective for storage engines that support transaction processing, such as InnoDB.
  2. Make sure the storage engine of the table is InnoDB when using transactions, or else the transaction will not work.
  3. In transaction processing, in case of an error or exception, you can use the ROLLBACK statement to rollback the transaction and ensure data integrity.
  4. When using the COMMIT statement to commit a transaction, it is important to be aware that deadlocks or long lock delays may arise in certain situations. Adjusting the transaction isolation level can help resolve these issues.
  5. In long-running transactions, it is important to ensure that the database’s log space is sufficient to prevent log overflow.
  6. During the development process, it is important to properly utilize transactions, avoid excessive locking, and long transaction processing times in order to improve system performance.
bannerAds