Advanced SQL Interview Questions
Advanced SQL Interview Questions Advanced SQL Interview Questions & Answers 1️⃣ Second Highest Salary (No TOP/LIMIT/RANK) You can use a subquery to find the second highest salary: SELECT MAX(salary) AS SecondHighest FROM employees WHERE salary This finds the maximum salary less than the overall maximum. 2️⃣ WHERE vs HAVING WHERE filters rows before aggregation. HAVING filters groups after aggregation. SELECT department, AVG(salary) FROM employees WHERE salary > 3000 GROUP BY department HAVING AVG(salary) > 5000; 3️⃣ Detect & Delete Duplicates Detect duplicates: SELECT name, COUNT(*) FROM employees GROUP BY name HAVING COUNT(*) > 1; Delete duplicates (keep one copy): DELETE FROM employees WHERE rowid NOT IN ( SELECT MIN(rowid) FROM employees GROUP BY name ); 4️⃣ Correlated vs Uncorrelated Subqueries Uncorrelated subquery runs independently. Correlated subquery...