Window: SELECT * FROM (SELECT *, MAX(salary) OVER (PARTITION BY department) AS dept_max FROM employees) t WHERE salary = dept_max. Correlated subquery: WHERE salary = (SELECT MAX(salary) FROM employees WHERE department = e.department). **Why window**: Single table scan;...
This medium-level SQL question appears frequently in data engineering interviews at companies like TCS. While less common, it tests deeper understanding that distinguishes strong candidates. Mastering the underlying concepts (partition, window) will help you answer variations of this question confidently.
Break this problem into components. Identify the core trade-offs involved, then walk the interviewer through your reasoning step by step. Demonstrate awareness of edge cases and production considerations - this is what separates good answers from great ones.
Window: SELECT FROM (SELECT , MAX(salary) OVER (PARTITION BY department) AS dept_max FROM employees) t WHERE salary = dept_max. Correlated subquery: WHERE salary = (SELECT MAX(salary) FROM employees WHERE department = e.department). Why window: Single table scan; correlated subquery can be O(n²). Multiple max-per-dept: Both return all employees tied for max. Performance: Index (department, salary) for large tables.
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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.