select
    PORT_CODE as "港コード",
    PORT_NAME as "港名",
    in_amt as "入国者数",
    out_amt as "出国者数",
    in_amt - out_amt as "差分"
from 
(
    select 
        i.PORT_CODE, 
        p.PORT_NAME, 
        i.KIND_CODE, 
        i.AMT as in_amt, 
        max(i.AMT) over (partition by i.PORT_CODE order by i.KIND_CODE rows between 1 following and 1 following) as out_amt
    from IMMIGRATION as i
        inner join PORT as p
        on i.PORT_CODE = p.PORT_CODE
    where i.group_code = 120
)
where in_amt > out_amt
order by 
    "差分" desc,
    "港コード" desc
;