SELECT
IM1.PORT_CODE AS 港コード
,PT.PORT_NAME AS 港名
,IM1.AMT AS 入国者数
,IM2.AMT AS 出国者数
,(IM1.AMT - IM2.AMT) AS 差分
FROM
IMMIGRATION AS IM1
INNER JOIN
IMMIGRATION AS IM2
ON 
IM1.PORT_CODE = IM2.PORT_CODE
AND IM1.GROUP_CODE = IM2.GROUP_CODE
AND IM2.KIND_CODE = '120'
INNER JOIN
PORT AS PT
ON IM1.PORT_CODE = PT.PORT_CODE
WHERE
IM1.GROUP_CODE = '120'
AND IM1.KIND_CODE = '110'
AND 差分 > 0
ORDER BY
差分 DESC
,IM1.PORT_CODE DESC