select 
    im110.PORT_CODE as 港コード
    , pr.PORT_NAME as 港名
    , im110.AMT as 入国者数
    , im120.AMT as 出国者数
    , im110.AMT - im120.AMT as 差分
from IMMIGRATION im110
  inner join PORT pr
    on pr.PORT_CODE = im110.PORT_CODE
  inner join IMMIGRATION im120
    on im120.PORT_CODE = im110.PORT_CODE
    and im120.KIND_CODE = 120
where
    im110.KIND_CODE = 110
    and 入国者数 > 出国者数
order by
    差分 desc
    , im110.PORT_CODE desc