select
t1.PORT_CODE,
p.PORT_NAME,
sum(t1.AMT) as "入国者数",
sum(t2.AMT) as "出国者数",
sum(t1.AMT) -sum(t2.AMT) as "差分"
from IMMIGRATION as t1
inner join PORT as p
on t1.PORT_CODE = p.PORT_CODE

inner join IMMIGRATION as t2
on t1.PORT_CODE = t2.PORT_CODE
and t2.KIND_CODE = "120"

where t1.KIND_CODE = "110"
and t1.AMT> t2.AMT

group by
t1.PORT_CODE
order by
差分 desc,t1.PORT_CODE desc