Top 7 SQL Interview Questions Asked at MAANG Companies

If you're targeting companies like Meta, Amazon, Apple, Netflix, and Google — SQL is not just about writing queries.
It’s about thinking in data, optimizing logic, and solving real-world problems.

Here are 7 must-know SQL questions (with detailed explanations) 👇

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1️⃣ Find the 2nd Highest Salary

💡 Problem:

Find the second highest salary from an employee table.

✅ Solution:

SELECT MAX(salary) AS second_highest
FROM employees
WHERE salary < (SELECT MAX(salary) FROM employees);

🧠 Why this matters:

• Tests understanding of subqueries
• Alternative approaches: DENSE_RANK(), LIMIT/OFFSET

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2️⃣ Find Duplicate Records

💡 Problem:

Identify duplicate rows based on email.

✅ Solution:

SELECT email, COUNT(*)
FROM users
GROUP BY email
HAVING COUNT(*) > 1;

🧠 What interviewer checks:

• Understanding of GROUP BY + HAVING
• Real-world use: fraud detection, data cleaning

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3️⃣ Get Top N Records Per Group

💡 Problem:

Find top 3 highest-paid employees per department.

✅ Solution:

SELECT *
FROM (
    SELECT *,
           DENSE_RANK() OVER (PARTITION BY department ORDER BY salary DESC) AS rnk
    FROM employees
) t
WHERE rnk <= 3;

🧠 Why it’s important:

• Tests window functions
• Very common in Amazon & Meta interviews

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4️⃣ Calculate Running Total

💡 Problem:

Find cumulative sales over time.

✅ Solution:

SELECT date,
       SUM(sales) OVER (ORDER BY date) AS running_total
FROM sales;

🧠 What this shows:

• Understanding of analytical functions
• Used in dashboards and reporting

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5️⃣ Find Missing Records (Gaps in Data)

💡 Problem:

Find missing IDs in a sequence.

✅ Solution:

SELECT t1.id + 1 AS missing_id
FROM table1 t1
LEFT JOIN table1 t2
ON t1.id + 1 = t2.id
WHERE t2.id IS NULL;

🧠 Why it matters:

• Tests joins + logical thinking
• Common in data integrity checks

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6️⃣ Customers Who Never Ordered

💡 Problem:

Find customers who have never placed an order.

✅ Solution:

SELECT c.customer_id
FROM customers c
LEFT JOIN orders o
ON c.customer_id = o.customer_id
WHERE o.customer_id IS NULL;

🧠 Interview focus:

• Understanding of LEFT JOIN + NULL filtering
• Real business use case

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7️⃣ Find Median Salary

💡 Problem:

Calculate median salary (tricky in SQL).

✅ Solution:

SELECT AVG(salary) AS median
FROM (
    SELECT salary,
           ROW_NUMBER() OVER (ORDER BY salary) AS rn,
           COUNT(*) OVER () AS total
    FROM employees
) t
WHERE rn IN (FLOOR((total+1)/2), CEIL((total+1)/2));

🧠 Why this is advanced:

• Combines window functions + math
• Often asked in Google interviews