select 單量區(qū)間 , count(distinct 客戶id) as 客戶數(shù) 
from (
  select 客戶id,單量,case when 單量 <= 5 then ‘0-5’ when 單量 >= 6 and 單量 <= 10 then ‘6-10’when 單量 >= 11 and 單量 <= 20          then ‘11-20’else ‘20以上’ end as 單量區(qū)間  
     from (
     select 客戶id,count(distinct 運單號) as 單量 
     from 快遞攬收表 
     where 創(chuàng)建日期 >= ‘2020-05-01’ and 創(chuàng)建日期 <= ‘2020-05-31’
     group by 客戶id) 
   as t1) 
as t2 
group by 單量區(qū)間;