题解 | 汇总各个部门当前员工的title类型的分配数目

select a.dept_no,dept_name,title ,count(*) 
from dept_emp as a
join titles as b
on a.emp_no=b.emp_no
join departments as c
on a.dept_no =c.dept_no
group by a.dept_no ,title,dept_name --筛选dept_no，title,dept_name
order by a.dept_no ,title 按照这两种进行排序