select 
i.port_code as '港コード'
,p.port_name as '港名'
,i.amt as '入国者数'
,i2.amt as '出国者数'
,i.amt-i2.amt as 差分
from immigration as i
inner join immigration as i2
on i2.port_code=i.port_code
and i2.group_code=i.group_code
and i2.kind_code='120'
inner join port as p
on p.port_code = i.port_code
where i.group_code ='120'
and i.kind_code ='110'
and i.amt-i2.amt >0
order by i.amt-i2.amt desc ,i.port_code desc