Transactions in MySQL: An Overview

Note: this page has been created with the use of AI. Please take caution, and note that the content of this page does not necessarily reflect the opinion of Cratecode.

Transactions, in the context of a database, are like a cozy safety blanket wrapped around our data. They make sure that our data stays consistent and secure, even when things go wrong. Transactions in MySQL let us group multiple tasks into a single unit of work that either completely succeeds or completely fails. No half-baked operations here!

Transactions: A Little Theory

Before we dive into the practical side of things, let's take a quick detour into the theory. The term transaction usually refers to a logical unit of work that contains one or more SQL commands. The effects of all the SQL statements in a transaction can be either all committed (applied to the database) or all rolled back (undone from the database).

The ACID Properties

Transactions are governed by four key properties, collectively known as the ACID properties. No, we’re not talking about the kind of acid you’d find in a chemistry lab, but rather Atomicity, Consistency, Isolation, and Durability.

These properties ensure that the transactions are processed reliably in a database system.

• Atomicity: This ensures that a transaction is treated as a single, indivisible unit, which either succeeds completely, or fails completely.

• Consistency: This ensures that a transaction brings the database from one valid state to another, maintaining the integrity of the data.

• Isolation: This ensures that concurrent execution of transactions leaves the database in the same state as if the transactions were executed sequentially.

• Durability: This ensures that once a transaction has been committed, it will remain committed even in the case of a system failure.

Managing Transactions in MySQL

In MySQL, we manage transactions with the help of three SQL commands: START TRANSACTION, COMMIT, and ROLLBACK.

• START TRANSACTION begins a new transaction.

• COMMIT commits the current transaction, making all changes made during the transaction permanent.

• ROLLBACK rolls back the current transaction, undoing any changes made during the transaction.

Here's an example of what a transaction might look like in MySQL:

START TRANSACTION;
UPDATE accounts SET balance = balance - 100 WHERE name = 'Alice';
UPDATE accounts SET balance = balance + 100 WHERE name = 'Bob';
COMMIT;

In this transaction, we're transferring 100 units from Alice's account to Bob's account. If something were to go wrong partway through (say, after deducting from Alice's account, but before adding to Bob's account), the transaction would be rolled back, and the database would remain as if nothing had happened. That's the power of transactions!

FAQ

START TRANSACTION;
UPDATE accounts SET balance = balance - 100 WHERE name = 'Alice';
UPDATE accounts SET balance = balance + 100 WHERE name = 'Bob';
COMMIT;