select
 va as 港コード,
 vb as 港名,
 vc as 入国者数,
 vd as 出国者数,
 vc-vd as 差分
from (
select
 i.PORT_CODE as va,
 p.PORT_NAME as vb,
 sum(case when kind_code = '110' then amt else 0 end) as vc,
 sum(case when kind_code = '120' then amt else 0 end) as vd,
 group_code
from
 IMMIGRATION as i
join
 PORT as p on i.port_code = p.port_code
group by 
 p.port_code, p.port_name, i.group_code
) as x
where 
 vc > vd and group_code = '120'
order by 
 差分 desc,
 va desc
;