PostgreSQL Transactions and Indexing: How COMMIT and ROLLBACK Keep Data Consistent

A tutorial introduces database transactions using an e-commerce example where a stock update could leave data inconsistent if the app crashes midway. It explains that a transaction groups related SQL operations so they either all succeed or all fail together. The article describes the three core commands, BEGIN to start, COMMIT to make changes permanent, and ROLLBACK to undo them, illustrated with a bank transfer and a laptop stock case. It positions transactions as the mechanism for keeping database state accurate, with indexing and SQLAlchemy topics covered later in the series.