Why are locks needed in databases?

Locks in databases are necessary to ensure data integrity and consistency when multiple transactions access the data simultaneously. They prevent race conditions where two processes try to modify the same data at the same time, which could lead to incorrect results.

The main purposes of locking:

• Transaction isolation: guarantees that parallel operations do not interfere with each other.
• Conflict prevention: lock rows or tables so that other transactions cannot modify them until the current one is finished.
• Ensuring atomicity: if a transaction does not complete successfully, its changes are not visible to others.

For example, if two users try to withdraw money from the same account at the same time, locking ensures that the operations are performed sequentially, and the balance does not go into negative due to parallel withdrawals.