SELECT
       IM.PORT_CODE AS '港コード'
       ,PT.PORT_NAME AS '港名'
       ,IM.AMT AS '入国者数'
       ,IM2.AMT AS '出国者数'
       ,(IM.AMT - IM2.AMT) AS '差分'
FROM
    IMMIGRATION AS IM

INNER JOIN
    IMMIGRATION AS IM2
    ON IM2.PORT_CODE = IM.PORT_CODE
    AND IM2.GROUP_CODE = '120'
    AND IM2.KIND_CODE = '120'
    
INNER JOIN
    PORT AS PT
ON
    PT.PORT_CODE = IM.PORT_CODE

    
WHERE 
    IM.GROUP_CODE = '120'
    AND IM.KIND_CODE = '110'
    AND 差分 > 0
ORDER BY
    差分 DESC
    ,IM.PORT_CODE DESC