How to select 10 random rows?
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
-- MySQL
SELECT * FROM tbl ORDER BY RAND() LIMIT 10;
-- PostgreSQL
SELECT * FROM tbl ORDER BY RANDOM() LIMIT 10;
-- SQL Server
SELECT TOP 10 * FROM tbl ORDER BY NEWID();
Performance note: This is O(n log n) and full table scan. For large tables, use a random ID approach.
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.