Hackforge Academy

Explanation

Rollback in a database is a transaction control operation that undoes all changes made during the current transaction. It restores the database to its previous consistent state before the transaction began.

Code:

-- Example
BEGIN;
UPDATE accounts SET balance = balance 
- 100 WHERE id = 1;
ROLLBACK; -- Cancels the update

Explanation

Rollback is needed to maintain data integrity when an error occurs during a transaction. If any step fails, rollback ensures that partial changes are not saved.

Code:

-- Transfer example
BEGIN;
UPDATE accounts SET balance = 
balance - 100 WHERE id = 1;
-- Suppose error happens here
ROLLBACK;

Explanation

It is also used to handle system failures, application crashes, or unexpected issues, ensuring the database remains consistent.

Code:

-- If system crashes before commit,
 DB automatically rolls back 
incomplete transactions

Explanation

Rollback is a key part of ACID properties (Atomicity), which ensures that a transaction is either fully completed or not applied at all.

Code:

-- Atomic transaction
BEGIN;
INSERT INTO orders VALUES (1, 'item');
ROLLBACK; -- No data inserted

Explanation

Real-time usage: Rollback is commonly used in banking systems, e-commerce transactions, and financial operations where partial updates can lead to incorrect data.

Code:

-- Safe transaction
BEGIN;
UPDATE wallet SET amount = amount - 
500 WHERE user_id = 10;

UPDATE wallet SET amount = amount +
 500 WHERE user_id = 20;
-- If any issue
ROLLBACK;
-- Else
COMMIT;