SELECT IM.PORT_CODE AS 港コード
       ,PT.PORT_NAME AS 港名
       ,IM.AMT AS 入国者数
       ,IMM.AMT AS 出国者数
       ,IM.AMT - IMM.AMT AS 差分
FROM  IMMIGRATION AS IM
inner join PORT AS PT
ON IM.PORT_CODE = PT.PORT_CODE
inner join (SELECT AMT
                  ,PORT_CODE
            FROM IMMIGRATION
            WHERE GROUP_CODE = 120
              AND  KIND_CODE = 120) AS IMM
ON IM.PORT_CODE = IMM.PORT_CODE
WHERE GROUP_CODE = 120
  AND KIND_CODE = 110
  AND IM.AMT > IMM.AMT
order by 差分 desc
       , IM.PORT_CODE desc