SELECT PO.PORT_CODE AS 港コード
,PO.PORT_NAME AS 港名
,IMIN.AMT AS 入国者数
,IM.AMT AS 出国者数
,IMIN.AMT - IM.AMT AS 差分
FROM IMMIGRATION AS IM
LEFT JOIN PORT AS PO
ON IM.PORT_CODE = PO.PORT_CODE
INNER JOIN IMMIGRATION AS IMIN
ON IM.PORT_CODE = IMIN.PORT_CODE 
AND IM.GROUP_CODE = IMIN.GROUP_CODE 
AND IMIN.KIND_CODE = '110'
WHERE IM.KIND_CODE='120'
AND 差分>0

ORDER BY 差分 desc
,港コード desc