SELECT
IM1.PORT_CODE AS 港コード,
IM2.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 PORT AS IM2 ON IM1.PORT_CODE = IM2.PORT_CODE
INNER JOIN GRP ON IM1.GROUP_CODE = IM2.GROUP_CODE
WHERE
IM1.GROUP_CODE = "110"
IM2.GROUP_CODE = "120"
差分 > 0
ORDER BY 
差分 DESC,
IM1.PORT_CODE DESC;