运行时间60ms 

Select distinct dept_no,dept_name,title,
(select count(title) from titles t1 where emp_no 
in (select emp_no from dept_emp de1 where de1.dept_no = de2.dept_no 
   and t1.title = t2.title)) 
as 'count'
from titles t2
join dept_emp de2  using(emp_no)
join departments using(dept_no)
order by dept_no,title

写的越来越不知道是什么了 只是能通过
再看题解发现用group by会好一点