SELECT email, COUNT(*) AS count  
FROM Users  
GROUP BY email  
HAVING COUNT(*) > 1;

SELECT *  
FROM Employees e  
WHERE salary = (  
  SELECT MAX(salary)  
  FROM Employees  
  WHERE department_id = e.department_id  
);

SELECT c.name, COUNT(o.id) AS total_orders  
FROM Customers c  
LEFT JOIN Orders o ON c.id = o.customer_id  
GROUP BY c.name;

SELECT p.name  
FROM Products p  
LEFT JOIN Sales s ON p.id = s.product_id  
WHERE s.product_id IS NULL;

SELECT * FROM Orders  
ORDER BY order_date DESC  
LIMIT 5;

SELECT * FROM Employees  
WHERE salary > (SELECT AVG(salary) FROM Employees);

SELECT  
  DATE_FORMAT(sale_date, '%Y-%m') AS month,  
  SUM(amount) AS total  
FROM Sales  
GROUP BY month;

SELECT customer_id, COUNT(*) AS count  
FROM Orders  
WHERE product = 'Laptop'  
GROUP BY customer_id  
HAVING COUNT(*) > 1;