What is phantom read in the context of transaction isolation levels?
2025
What is phantom read in the context of transaction isolation levels?
- A.
A transaction reads a set of rows that were inserted by another transaction after it started
- B.
A transaction reads data that was committed by another transaction
- C.
A transaction reads data that was changed by another transaction but not yet committed
- D.
None of the above
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Correct answer: A
A phantom read occurs when a transaction re-executes a query and finds new rows inserted by another committed transaction since the first execution. This phenomenon typically happens at lower isolation levels like Read Committed, where locking mechanisms do not prevent new rows from appearing in result sets.