Find Employees Below Department Average Salary

Question

Find employees whose salary is less than the average salary of their department.

Accepted Answer

```sql
SELECT e.id, e.name, e.salary, e.department_id
FROM employees e
WHERE e.salary < (
    SELECT AVG(salary)
    FROM employees
    WHERE department_id = e.department_id
);
```

This query uses a correlated subquery to calculate the average salary for each employee's specific department and filters for those whose salary is strictly less than that calculated average.