select area,e_id,e_name,数量,rank_num from
(select b.e_id,count(b.b_id) as 数量,area,e.e_name,rank()over(partition by area order by count(b.b_id) desc) as rank_num
 from  bill_info b left join employee_info e on b.e_id=e.e_id 
where year(date)=2019 and month(date)=8 group by area,b.e_id)t where 10<=rank_num<=20;