Transactions, ACID, Locking, Concurrency, and Consistency
Handle critical business updates safely by understanding transactional behavior in MySQL.
Inside this chapter
- Why Transactions Matter
- ACID Principles
- Basic Transaction Flow
- Locking and Concurrency
- Business Example
Series navigation
Study the chapters in order for the clearest path from MySQL basics to advanced performance, consistency, and production operations. Use the navigation at the bottom to move smoothly through the full tutorial series.
Why Transactions Matter
Many systems must ensure that related changes succeed together or fail together. Payments, inventory adjustments, transfers, and order workflows are classic examples where partial success would be dangerous.
ACID Principles
- Atomicity: all or nothing
- Consistency: valid state before and after
- Isolation: concurrent transactions should not corrupt each other
- Durability: committed data should survive failures appropriately
Basic Transaction Flow
START TRANSACTION;
UPDATE accounts SET balance = balance - 100 WHERE id = 1;
UPDATE accounts SET balance = balance + 100 WHERE id = 2;
COMMIT;Locking and Concurrency
Multiple users and services may update data simultaneously. MySQL must coordinate these interactions carefully to preserve correctness. Understanding isolation and locking helps explain why some applications see contention or inconsistent reads.
Business Example
A wallet transfer system cannot allow money to be removed from one account without reaching the destination account. Transactional correctness is central to trust in such systems.