# Dirty Read

__*Dirty Read*__

![`smart`](DirtyReadExample_en_001_20220428.png)

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In the example in the slide:
- Transaction A updates the value of TicketCount to 10 to reflect a customer purchase. Then it commences the billing process.
- While Transaction A is still in progress, Transaction B starts. It reads the TicketCount value which is 10 at the time the read occurs.
- Transaction A then fails because the customer's payment is declined and TicketCount is rolled back to its original value of 11. However, Transaction B is working on the basis that the value of TicketCount is 10.
- Transaction B has read an uncommitted change from another transaction. This is known as a "dirty read."