select
  PORT_CODE as '港コード',
  PORT_NAME as '港名',
  IN_AMT as '入国者数',
  OUT_AMT as '出国者数',
  IN_AMT - OUT_AMT as '差分'
from (
  select
    im.PORT_CODE,
    po.PORT_NAME,
    SUM(CASE WHEN im.KIND_CODE = 110 THEN im.AMT ELSE 0 END) as IN_AMT,
    SUM(CASE WHEN im.KIND_CODE = 120 THEN im.AMT ELSE 0 END) as OUT_AMT
  from
    IMMIGRATION im
  join
    PORT po
    on im.PORT_CODE = po.PORT_CODE
  join
    GRP gr
    on im.GROUP_CODE = gr.GROUP_CODE
  where
    gr.GROUP_NAME = '外国人'
  group by
    im.PORT_CODE,
    po.PORT_NAME
) as sub
where
  IN_AMT > OUT_AMT
order by
  IN_AMT - OUT_AMT desc,
  PORT_CODE desc
;