select
  district_name as "都道府県名",
  sum(total_amt) as "総人口"

from (

  select
    floor(district_code / 1000) as dist_cd,
    district_name,
    total_amt

  from
    population
  ) p

where
  p.dist_cd <> 0

group by
  dist_cd

order by
  sum(total_amt) desc