What are some examples of lost updates in SQL?

What are some examples of lost updates in SQL?

Lost updates occur when two transactions read the same data and then update it, leading to one update being lost. For example, if Transaction A reads a value, then Transaction B reads the same value and updates it, when Transaction A finally updates the value, it overwrites Transaction B's update.

Can you give me a specific scenario?

Sure! Imagine two bank transactions: Transaction A checks an account balance of $100 and decides to withdraw $50. At the same time, Transaction B also checks the same balance and withdraws $30. If Transaction A updates the balance to $50, it overwrites Transaction B's update, which should have set the balance to $70.

How can I prevent lost updates in SQL?

You can prevent lost updates by using locking mechanisms, such as optimistic or pessimistic locking, or by implementing version control for your records.

What is optimistic locking?

Optimistic locking allows multiple transactions to proceed without locking the data initially. Before committing, it checks if the data has been modified by another transaction. If it has, the transaction is rolled back.