Write an SQL query that lists all departments where the average salary is greater than 60,000.

Group the employees by department, calculate the average salary, and filter with HAVING:

SELECT department,
       AVG(salary) AS avg_salary
FROM   Employees
GROUP BY department
HAVING AVG(salary) > 60000;

This query performs a single aggregation pass over the table, so its time complexity is O(n). It returns each department that meets the threshold along with the computed average salary.