SELECT 
	 P.port_code AS 港コード
	,P.port_name AS 港名
	,SUM(
		CASE I.kind_code
			WHEN '110' THEN IFNULL(I.AMT,0)
		END
	) AS 入国者数
	,SUM(
		CASE I.kind_code
			WHEN '120' THEN IFNULL(I.AMT, 0)
		END
	) AS 出国者数
	,SUM(
		CASE I.kind_code
			WHEN '110' THEN IFNULL(I.AMT, 0)
			WHEN '120' THEN -1 * IFNULL(I.AMT, 0)
		END
	) 差分
FROM
	Port P
INNER JOIN
	IMMIGRATION I	
ON
	P.port_code = I.port_code
INNER JOIN
	GRP G
ON
	G.group_code = I.group_code
GROUP BY
	P.port_code	
HAVING
    差分 > 0
ORDER BY
    差分 DESC 
   ,港コード DESC