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