with target as (
    select
        i.port_code as port_code,
        p.port_name as port_name,
        sum(case when i.group_code="120" and i.kind_code="110" then i.amt else 0 end) as in_amt,
        sum(case when i.group_code="120" and i.kind_code="120" then i.amt else 0 end) as out_amt
    from
        immigration as i
        join
            grp as g
            on
                g.group_code = i.group_code
        join
            port as p
            on
                p.port_code = i.port_code
    group by
        i.port_code
)

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
    target as t
where
    "差分" > 0
order by
    "差分" desc,
    t.port_code desc