[Solved] Consider two transactions running concurrently on a table Orders. Transaction 1 reads all rows where status = 'pending'.... If Transaction 1 repeats the read, what phenomenon might it observe? | SQL

SQL - Transactions and Data Integrity

Consider two transactions running concurrently on a table Orders. Transaction 1 reads all rows where status = 'pending'. Transaction 2 inserts a new row with status = 'pending' and commits. If Transaction 1 repeats the read, what phenomenon might it observe?

ADirty read

BNon-repeatable read

CPhantom read

DLost update

Step-by-Step Solution

Solution:

Step 1: Analyze the scenario with inserted rows
Transaction 1 reads rows with status 'pending'. Transaction 2 inserts a new 'pending' row and commits.
Step 2: Identify the phenomenon on repeated read
When Transaction 1 reads again, it sees the new row that wasn't there before. This is a phantom read, where new rows appear between reads.
Final Answer:
Phantom read -> Option C
Quick Check:
New rows appearing = Phantom read [OK]

Quick Trick: New rows between reads = phantom read [OK]

Common Mistakes:

Confusing phantom read with dirty read
Thinking non-repeatable read applies to new rows
Mixing lost update with read phenomena

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More SQL Quizzes

If Transaction 1 repeats the read, what phenomenon might it observe?

Step 1: Analyze the scenario with inserted rows

Step 2: Identify the phenomenon on repeated read

Final Answer:

Quick Check:

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