What consequences may arise if a transaction is not completed successfully and is rolled back?

If a transaction is not completed successfully and is rolled back, the following consequences may occur:

• Cancellation of all changes: all operations performed within the transaction will be canceled, ensuring data integrity.

• Maintaining data consistency: the database or system reverts to the state before the transaction began, preventing partially applied changes.

• Data loss: if the transaction included important changes, they will not be saved, which may require re-executing the operation.

• Possible locks: in some systems, rolling back a transaction may lead to temporary resource locks, which can affect performance.

• Error handling necessity: the application must correctly handle transaction rollback to avoid failures and ensure proper behavior.

Example in PHP using PDO:

try {
    $pdo->beginTransaction();
    // Execute queries
    $pdo->commit();
} catch (Exception $e) {
    $pdo->rollBack(); // rollback transaction
    echo "Error: " . $e->getMessage();
}