select 
    p.PORT_CODE as 港コード
    ,p.PORT_NAME as 港名
    ,i1.AMT as 入国者数
    ,i2.AMT as 出国者数
    ,i1.AMT - i2.AMT as 差分
from PORT p
join IMMIGRATION i1 on i1.PORT_CODE == p.PORT_CODE and  i1.GROUP_CODE == '120' and i1.KIND_CODE = '110'
join IMMIGRATION i2 on i2.PORT_CODE == p.PORT_CODE and i2.GROUP_CODE == '120'  and  i2.KIND_CODE = '120'
where 差分 > 0
group by p.PORT_CODE
order by 差分 desc, p.PORT_CODE desc;