题解 | 汇总各个部门当前员工的title类型的分配数目

select 
    d.dept_no ,
    d.dept_name ,
    t.title ,
    count(title) as count
from departments d
join dept_emp de on d.dept_no = de.dept_no
join titles t on de.emp_no = t.emp_no
group by d.dept_no ,d.dept_name ,t.title
order by dept_no ,title