What is the CASE function?
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
SQL's version of IF-THEN-ELSE. Two forms: simple and searched.
-- Searched CASE (more flexible)
SELECT name,
CASE
WHEN salary >= 100000 THEN 'Executive'
WHEN salary >= 60000 THEN 'Senior'
WHEN salary >= 40000 THEN 'Mid'
ELSE 'Junior'
END AS level
FROM employees;
-- Simple CASE
SELECT name,
CASE dept
WHEN 'Engineering' THEN 'Tech'
WHEN 'Sales' THEN 'Revenue'
ELSE 'Other'
END AS dept_category
FROM employees;
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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.