select
 IM.PORT_CODE as 港コード
,PO.PORT_NAME as 港名
,SUM(CASE WHEN IM.KIND_CODE = 110 THEN AMT ELSE 0 END) as 入国者数
,SUM(CASE WHEN IM.KIND_CODE = 120 THEN AMT ELSE 0 END) as 出国者数
,SUM(CASE WHEN IM.KIND_CODE = 110 THEN AMT ELSE 0 END) - SUM(CASE WHEN IM.KIND_CODE = 120 THEN AMT ELSE 0 END) as 差分
from IMMIGRATION IM
inner join PORT PO
on IM.PORT_CODE = PO.PORT_CODE
group by
 IM.PORT_CODE
,PO.PORT_NAME
having 
SUM(CASE WHEN IM.KIND_CODE = 110 THEN AMT ELSE 0 END) - SUM(CASE WHEN IM.KIND_CODE = 120 THEN AMT ELSE 0 END) > 0
order by
 差分 desc
,港コード desc