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