[Solved] Given these two transactions:Transaction A: LOCK Table X; LOCK Table Y;Transaction B: LOCK Table Y; LOCK Table X;What problem can arise when both run simultaneously? | SQL

SQL - Transactions and Data Integrity

Given these two transactions:
Transaction A: LOCK Table X; LOCK Table Y;
Transaction B: LOCK Table Y; LOCK Table X;
What problem can arise when both run simultaneously?

AData inconsistency due to lost updates

BNo conflict, transactions will execute sequentially

CDeadlock due to cyclic locking dependencies

DAutomatic rollback of both transactions without delay

Step-by-Step Solution

Solution:

Step 1: Identify locking order
Transaction A locks Table X then Y; Transaction B locks Table Y then X.
Step 2: Analyze concurrency
If both start simultaneously, each may hold one lock and wait for the other, causing deadlock.
Final Answer:
Deadlock due to cyclic locking dependencies -> Option C
Quick Check:
Opposite lock order causes deadlock [OK]

Quick Trick: Opposite lock order causes deadlock [OK]

Common Mistakes:

Assuming transactions will queue automatically
Confusing deadlock with data inconsistency
Believing rollback happens immediately without detection

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More SQL Quizzes

Given these two transactions:

Step 1: Identify locking order

Step 2: Analyze concurrency

Final Answer:

Quick Check:

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