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Single Answer
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Which one of the following database issues occurs when one transaction writes a value to the database that overwrites a value that was needed by transactions with earlier precedence?

Answer Options

A

Dirty read

B

Incorrect summary

C

Lost update

D

SQL injection

Correct Answer: C

Explanation

Lost updates occur when one transaction writes a value to the database that overwrites a value needed by transactions that have earlier precedence, causing those transactions to read an incorrect value. Dirty reads occur when one transaction reads a value from a database that was written by another transaction that did not commit. Incorrect summaries occur when one transaction is using an aggregate function to summarize data stored in a database while a second transaction is making modifications to the database, causing the summary to include incorrect information. SQL injection is a web application security flaw, not a database concurrency problem.