SELECT DISTINCT T2.department_name FROM employees AS T1 JOIN departments AS T2 ON T1.department_id  =  T2.department_id
What are the names of departments that have at least one employee.
SELECT DISTINCT T2.department_name FROM employees AS T1 JOIN departments AS T2 ON T1.department_id = T2.department_id
select distinct t2 . department_name from employees as t1 join departments as t2 on t1 . department_id = t2 . department_id
What are the names of departments that have at least one employee .