select
     i.PORT_CODE as 港コード,
     p.PORT_NAME as 港名,
    sum(CASE WHEN i.KIND_CODE = '110' THEN i.AMT ELSE 0 END) AS 入国者数,
    sum(CASE WHEN i.KIND_CODE = '120' THEN i.AMT ELSE 0 END) AS 出国者数,
    sum(CASE WHEN i.KIND_CODE = '110' THEN i.AMT ELSE 0 END) - sum(CASE WHEN i.KIND_CODE = '120' THEN i.AMT ELSE 0 END) as 差分
from IMMIGRATION i 
    inner join GRP g
        on g.GROUP_CODE = i.GROUP_CODE
    inner join PORT p
        on p.PORT_CODE = i.PORT_CODE
where 
    i.GROUP_CODE = '120'
group by 
    i.PORT_CODE,
    p.PORT_NAME
having
    sum(CASE WHEN i.KIND_CODE = '110' THEN i.AMT ELSE 0 END) > sum(CASE WHEN i.KIND_CODE = '120' THEN i.AMT ELSE 0 END)
order by 
    差分 desc,
    i.PORT_CODE desc;