SELECT
	港コード
	,港名
	,入国者数
	,出国者数
	,入国者数 - 出国者数 as 差分
FROM
	(
		SELECT
			i.PORT_CODE as 港コード
			,p.PORT_NAME as 港名
			,SUM(CASE WHEN g.GROUP_CODE = 120 AND i.KIND_CODE = 110 THEN AMT ELSE 0 END) as 入国者数
			,SUM(CASE WHEN g.GROUP_CODE = 120 AND i.KIND_CODE = 120 THEN AMT ELSE 0 END) as 出国者数
		FROM
			IMMIGRATION as i
		INNER JOIN
			PORT as p
		ON
			i.PORT_CODE = p.PORT_CODE
		INNER JOIN
			GRP as g
		ON
			i.GROUP_CODE = g.GROUP_CODE
		GROUP BY
			港コード
			,港名		
	)
WHERE	
	入国者数 - 出国者数 > 0
ORDER BY
	差分 DESC
	,港コード DESC