create a table with a column for department id and a column for department name
select department_id,department_name from departments
Show the total number of employee ids for each department id
select t1.department_id, count ( * ) from departments as t1 join employees as t2 where t1.department_id = t2.department_id group by t1.department_id
Add a column with department name
select t1.department_id, t1.department_name, count ( * ) from departments as t1 join employees as t2 where t1.department_id = t2.department_id group by t1.department_id