select 
  p.PORT_CODE as "港コード",
  p.PORT_NAME as "港名",
  sum(case when KIND_CODE = "110" then AMT else 0 end) as "入国者数",
  sum(case when KIND_CODE = "120" then AMT else 0 end) as "出国者数",
  (sum(case when KIND_CODE = "110" then AMT else 0 end) - sum(case when KIND_CODE = "120" then AMT else 0 end)) as "差分"
from PORT as p
join IMMIGRATION as i on p.PORT_CODE = i.PORT_CODE
join GRP as g on i.GROUP_CODE = g.GROUP_CODE
where 
  g.GROUP_NAME = "外国人"
group by p.PORT_CODE
having "入国者数" > "出国者数"
order by "差分" desc, p.PORT_CODE desc
;