1️⃣ Find the second highest salary:
SELECT MAX(salary)
FROM employees
WHERE salary < (SELECT MAX(salary) FROM employees);
2️⃣ Count employees in each department:
SELECT department, COUNT(*)
FROM employees
GROUP BY department;
3️⃣ Fetch duplicate emails:
SELECT email, COUNT(*)
FROM users
GROUP BY email
HAVING COUNT(*) > 1;
4️⃣ Join orders with customer names:
SELECT c.name, o.order_date
FROM customers c
JOIN orders o ON c.id = o.customer_id;
5️⃣ Get top 3 highest salaries:
SELECT DISTINCT salary
FROM employees
ORDER BY salary DESC
LIMIT 3;
6️⃣ Retrieve latest 5 logins:
SELECT * FROM logins
ORDER BY login_time DESC
LIMIT 5;
7️⃣ Employees with no manager:
SELECT name
FROM employees
WHERE manager_id IS NULL;
8️⃣ Search names starting with ‘S’:
SELECT * FROM employees
WHERE name LIKE 'S%';
9️⃣ Total sales per month:
SELECT MONTH(order_date) AS month, SUM(amount)
FROM sales
GROUP BY MONTH(order_date);
🔟 Delete inactive users:
DELETE FROM users
WHERE last_active < '2023-01-01';
✅ Tip: Master subqueries, joins, groupings & filters – they show up in nearly every interview!
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