select  im.port_code as 港コード,
        port.port_name as 港名,
        sum(case when im.group_code = "120" and im.kind_code = "110" then im.amt end) as 入国者数,
        sum(case when im.group_code = "120" and im.kind_code = "120" then im.amt end) as 出国者数,
        sum(case when im.group_code = "120" and im.kind_code = "110" then im.amt end) - 
            sum(case when im.group_code = "120" and im.kind_code = "120" then im.amt end) as 差分
from immigration as im
inner join port on im.port_code = port.port_code
inner join grp on im.group_code = grp.group_code
group by 港コード
having 差分 > 0
order by 差分 desc,港コード desc;