with tmp as (
    select
    	P.PORT_CODE 
    	, P.PORT_NAME
    	, sum(case when I.KIND_CODE = '110' then AMT else 0 end) as IN_CNT
    	, sum(case when I.KIND_CODE = '120' then AMT else 0 end) as OUT_CNT
    	, sum(case when I.KIND_CODE = '110' then AMT else 0 end) 
    	    - sum(case when I.KIND_CODE = '120' then AMT else 0 end) as DIFF
    from PORT as P
    inner join IMMIGRATION as I using(PORT_CODE)
    group by P.PORT_CODE
)

select
    PORT_CODE as '港コード'
    , PORT_NAME as '港名'
    , IN_CNT as '入国者数'
    , OUT_CNT as '出国者数'
    , DIFF as '差分'
from tmp
where DIFF > 0
order by DIFF desc, PORT_CODE desc;