SELECT PT.PORT_CODE AS 港コード
,PT.PORT_NAME AS 港名
,IMNIN.AMT AS 入国者数
,IMNOUT.AMT AS 出国者数
,IMNIN.AMT - IMNOUT.AMT AS 差分
FROM IMMIGRATION AS IMN
LEFT JOIN PORT AS PT
       ON IMN.PORT_CODE = PT.PORT_CODE
LEFT JOIN GRP AS GP
       ON IMN.GROUP_CODE = GP.GROUP_CODE
       AND GP.GROUP_CODE=120
INNER JOIN IMMIGRATION AS IMNIN
        ON IMN.PORT_CODE = IMNIN.PORT_CODE
        AND IMNIN.KIND_CODE
INNER JOIN IMMIGRATION AS IMNOUT
        ON IMN.PORT_CODE = IMNOUT.PORT_CODE
        AND IMNOUT.KIND_CODE
WHERE 差分>0
  AND IMN.KIND_CODE=120
GROUP BY PT.PORT_CODE
ORDER BY 差分 DESC,港コード DESC