select 
port.PORT_CODE as "港コード",
port.PORT_NAME as "港名",
SUM(case imi.KIND_CODE when "110" then AMT else 0 end) as "入国者数",
SUM(case imi.KIND_CODE when "120" then AMT else 0 end) as "出国者数",
SUM(case imi.KIND_CODE when "110" then AMT else 0 end)-SUM(case imi.KIND_CODE when "120" then AMT else 0 end) as "差分"
from IMMIGRATION as imi
inner join PORT as port
on imi.PORT_CODE=port.PORT_CODE
where imi.GROUP_CODE="120"
group by imi.PORT_CODE
having SUM(case imi.KIND_CODE when "110" then AMT else 0 end)-SUM(case imi.KIND_CODE when "120" then AMT else 0 end)>0
order by "差分" desc,"港コード" desc;