Select
	a.port_code as 港コード,
	a.port_name as 港名,
	sum(case when b.kind_code = 110 then b.amt else 0 end) as 入国者数,
	sum(case when b.kind_code = 120 then b.amt else 0 end) as 出国者数,
	sum(case when b.kind_code = 110 then b.amt else 0 end) - sum(case when b.kind_code = 120 then b.amt else 0 end) as 差分
From
	immigration as b
	inner join port as a
		on (a.port_code = b.port_code)
	inner join grp as c
		on (c.group_code = b.group_code)
Where
	c.group_name = '外国人'
group by a.port_code, a.port_name
having 差分 > 0
Order by 
5 desc, 1 desc