UPDATE employees SET gender = CASE gender WHEN 'M' THEN 'F' WHEN 'F' THEN 'M' ELSE gender END. For SELECT: SELECT id, name, CASE gender WHEN 'M' THEN 'F' WHEN 'F' THEN 'M' ELSE gender END AS gender FROM employees. **Why**: ELSE preserves NULL/other values....
This easy-level SQL question appears frequently in data engineering interviews at companies like Fossil Group. While less common, it tests deeper understanding that distinguishes strong candidates.
Start by clearly defining the core concept being asked about. Interviewers want to see that you understand the fundamentals before diving into implementation details. Structure your answer with a definition, then explain the practical application with a concise example.
UPDATE employees SET gender = CASE gender WHEN 'M' THEN 'F' WHEN 'F' THEN 'M' ELSE gender END. For SELECT: SELECT id, name, CASE gender WHEN 'M' THEN 'F' WHEN 'F' THEN 'M' ELSE gender END AS gender FROM employees. Why: ELSE preserves NULL/other values. Best practice: Handle NULL; audit logging for sensitive changes; immutable approach (new column) for compliance.
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Analyze My Answer — FreeAccording to DataEngPrep.tech, this is one of the most frequently asked SQL interview questions, reported at 1 company. DataEngPrep.tech maintains a curated database of 1,863+ real data engineering interview questions across 7 categories, verified by industry professionals.