🔥 SQL Scenario-Based Interview Q&A (Most Asked 💯)

Think like a Data Analyst 👇

📊 Q1. Find the Nth highest salary (not just 2nd/3rd)?

👉 Use DENSE_RANK() or ROW_NUMBER()
👉 Filter where rank = N
👉 Handle duplicates carefully

📊 Q2. Find common records between two tables?

👉 Use INNER JOIN
👉 Or INTERSECT (if supported)
👉 Based on matching columns

📊 Q3. Find records present in both tables but with different values?

👉 JOIN on key
👉 Compare columns in WHERE
👉 Useful for data mismatch checks

📊 Q4. Count number of orders per day + running total?

👉 GROUP BY order_date
👉 Use SUM() OVER (ORDER BY date)

📊 Q5. Find users who never placed any order?

👉 LEFT JOIN orders
👉 Filter WHERE order_id IS NULL
👉 Or use NOT EXISTS

📊 Q6. How do you delete duplicate rows but keep one?

👉 Use ROW_NUMBER() with PARTITION BY
👉 Delete where row_number > 1
👉 Always test with SELECT first ⚠️
👉 Backup before deleting


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