CREATE TEMPORARY TABLE temp AS
SELECT PORT_CODE AS PORT_CODE,
SUM(CASE KIND_CODE WHEN '110' THEN AMT ELSE 0 END) AS in_member,
SUM(CASE KIND_CODE WHEN '120' THEN AMT ELSE 0 END) AS out_member
FROM IMMIGRATION
JOIN GRP ON IMMIGRATION.GROUP_CODE = GRP.GROUP_CODE
where GRP.GROUP_NAME = '外国人'
group by PORT_CODE;

select 
temp.PORT_CODE AS 港コード,
PORT.PORT_NAME AS 港名,
temp.in_member AS 入国者数,
temp.out_member AS 出国者数,
abs(temp.out_member - temp.in_member) AS 差分
FROM temp
JOIN PORT ON PORT.PORT_CODE = temp.PORT_CODE
group by temp.PORT_CODE
order by 5 desc, 1 desc;