Explain the concept of transaction rollback

Transaction rollback is the process of undoing all changes made during a transaction to return the database to its state before the transaction began. It is used to maintain data integrity and consistency in the following scenarios:

1. **Error Handling:** If an error occurs during transaction execution, a rollback undoes all operations to prevent partial or incorrect data modifications.

2. **Validation Failures:** If a transaction fails to meet certain validation criteria or constraints, a rollback ensures that none of the changes are applied.

3. **Manual Intervention:** An explicit rollback command can be issued if the transaction needs to be aborted by the user or application.

4. **System Failures:** In the event of a system crash or failure, a rollback can be triggered to recover and restore the database to a consistent state using transaction logs.

Rollback is essential for preserving data integrity and consistency by ensuring that only fully completed and validated transactions affect the database.