select a.PORT_CODE as 港コード,
a.PORT_NAME as 港名,
b.c as 入国者数,
e.d as 出国者数,
(b.c - e.d) as 差分
from PORT a
join (select PORT_CODE, sum(AMT) as c from IMMIGRATION
where KIND_CODE = "110" and GROUP_CODE = "120" group by PORT_CODE ) b on a.PORT_CODE = b.PORT_CODE
join (select PORT_CODE, sum(AMT) as d from IMMIGRATION
where KIND_CODE = "120" and GROUP_CODE = "120" group by PORT_CODE) e on a.PORT_CODE = e.PORT_CODE
where 差分 > 0
order by 差分 desc,港コード desc