START TRANSACTION - MySQL

Overview

START TRANSACTION initiates a new database transaction. It establishes a savepoint that marks the beginning of a group of database operations that should be treated as a single logical unit. If the transaction is successful, all changes made within it will be committed to the database; otherwise, they will be rolled back.

Syntax

START TRANSACTION [WITH CONSISTENT SNAPSHOT]

Options

  • WITH CONSISTENT SNAPSHOT: Ensures that the data read during the transaction is consistent even if other transactions are modifying the same data concurrently.

Examples

Simple Transaction:

START TRANSACTION;
INSERT INTO users (name) VALUES ('John Doe');
COMMIT;

Transaction with Consistent Snapshot:

START TRANSACTION WITH CONSISTENT SNAPSHOT;
SELECT * FROM users WHERE name = 'John Doe';  -- Reads consistent data
...
COMMIT;

Transaction with Rollback:

START TRANSACTION;
INSERT INTO users (name) VALUES ('John Doe');
ROLLBACK;  -- Undoes the changes

Common Issues

  • Deadlocks: Transactions can deadlock if they try to acquire the same locks in different orders. Use SET TRANSACTION ISOLATION LEVEL READ COMMITTED to reduce the risk of deadlocks.
  • Transaction Aborts: Transactions can abort due to errors, such as duplicate key violations or constraint violations. Handle these errors gracefully and provide informative error messages.
  • Long-Running Transactions: Keep transactions as short as possible to avoid the accumulation of locks and potential performance issues.

Integration

  • Stored Procedures: Transactions can be used within stored procedures to ensure data consistency across multiple queries.
  • Database Triggers: Transactions can be automatically started and committed when triggers are fired.
  • Replication: Transactions are replicated to slave servers to ensure data consistency across the cluster.
  • COMMIT: Commits the changes made within a transaction.
  • ROLLBACK: Undoes the changes made within a transaction.
  • SAVEPOINT: Creates a named savepoint within a transaction.
  • RELEASE SAVEPOINT: Releases a named savepoint.