Most Asked SQL Queries in Interviews (With Logic & Best Practices)

SQL interviews don’t require 100+ queries — just 25–30 practical ones that reflect real-world scenarios. But don’t just memorize them — understand the logic behind each.

This guide covers the most commonly asked SQL queries in technical interviews for roles like backend developers, data analysts, and full-stack engineers.

---

1️⃣ Get the 2nd Highest Salary

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

📌 Logic: Get the maximum salary that is less than the highest.

---

2️⃣ Find Duplicate Records

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

📌 Logic: Group by the field (e.g. email), then filter groups that occur more than once.

---

3️⃣ Count Employees Per Department

SELECT department, COUNT(*) 
FROM employees 
GROUP BY department;

---

4️⃣ Employees Who Didn't Submit Reports

SELECT name 
FROM employees 
WHERE id NOT IN (SELECT employee_id FROM reports);

📌 Logic: Use NOT IN with a subquery to filter missing entries.

---

5️⃣ Customers With More Than 2 Orders

SELECT customer_id 
FROM orders 
GROUP BY customer_id 
HAVING COUNT(*) > 2;

---

6️⃣ Top 3 Highest-Paid Employees

SELECT * 
FROM employees 
ORDER BY salary DESC 
LIMIT 3;

---

7️⃣ Join Orders With Customers

SELECT o.id, o.date, c.name 
FROM orders o 
JOIN customers c ON o.customer_id = c.id;

📌 Logic: Use JOIN to fetch customer names for each order.

---

8️⃣ Orders From the Last 7 Days

SELECT * 
FROM orders 
WHERE order_date >= CURRENT_DATE - INTERVAL 7 DAY;

---

9️⃣ Users Without Phone Numbers

SELECT * 
FROM users 
WHERE phone IS NULL;

---

🔟 Departments With Avg Salary > 50K

SELECT department, AVG(salary) 
FROM employees 
GROUP BY department 
HAVING AVG(salary) > 50000;

📌 Tip: Use HAVING with aggregates like AVG().

---

1️⃣1️⃣ Employees and Their Managers (Self Join)

SELECT e.name AS employee, m.name AS manager 
FROM employees e 
LEFT JOIN employees m ON e.manager_id = m.id;

---

1️⃣2️⃣ Customers With No Orders

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

---

1️⃣3️⃣ Month-Wise Sales Summary

SELECT MONTH(order_date) AS month, SUM(amount) AS total_sales 
FROM orders 
GROUP BY MONTH(order_date);

---

1️⃣4️⃣ Update NULL City to Default

UPDATE users 
SET city = 'Unknown' 
WHERE city IS NULL;

---

1️⃣5️⃣ Delete Duplicate Rows (Keep One)

DELETE FROM users 
WHERE id NOT IN (
  SELECT MIN(id) 
  FROM users 
  GROUP BY email
);

📌 Logic: Keep the record with the minimum ID per group (e.g. email).

---

💡 Pro Interview Tips

✅ Explain your logic out loud:

"First we JOIN the tables, then FILTER the results, and finally AGGREGATE based on the group..."

✅ Avoid SELECT * — Always select only needed columns
✅ Use aliases for clarity (e, o, c, etc.)
✅ Ask clarifying questions if unsure — interviews are collaborative

---

Mastering SQL isn’t about memorizing syntax — it’s about understanding how data flows, how to query with intent, and how to communicate your logic clearly.

Practice these queries
Save this article
Share it with your friends preparing for SQL interviews

👉 Bookmark this blog for quick revision before your next interview!

---

👉 Found this helpful? Follow DevDaily for more developer blogs every week!

✍ Written by Rishabh Mishra