What does ROLLBACK do after COMMIT?
Interviewer Expectations for this Question
01
Core Competency
Assesses fundamental understanding of SQL & Databases conventions, runtime behavior, and memory/performance considerations.
02
Evaluation Criteria
Hiring managers look for precision, avoidance of ambiguous jargon, and ability to explain trade-offs under real production conditions.
Comprehensive Model Answer
Verified Solution
ROLLBACK does nothing after a COMMIT has executed.
### Why?
Once a transaction issues COMMIT, the changes are permanently written to the database transaction log and storage engine. The transaction boundary is closed.
A subsequent ROLLBACK has no active transaction to undo and cannot revert committed transactions. Undoing committed data requires manual compensation transactions or point-in-time backup restoration.
Candidate Response Strategy & Interview Tips
- Start with a concise one-sentence summary: Deliver a direct, confident answer first before expanding into nuances.
- Demonstrate real-world trade-offs: Discuss where this approach excels and when you would avoid it in production systems.
- Discuss complexity & edge cases: Proactively explain time/space complexity or boundary conditions (null values, scale limits).
- Prepare for interviewer follow-ups: Technical hiring panels frequently probe deeper into concurrency, backward compatibility, or alternative libraries.