SELECT
    IM1.PORT_CODE AS '港コード',
    PT.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
    JOIN IMMIGRATION AS IM2
        ON IM1.PORT_CODE = IM2.PORT_CODE
        AND IM1.GROUP_CODE = IM2.GROUP_CODE
        AND IM2.KIND_CODE = '120'
    JOIN PORT AS PT
        ON PT.PORT_CODE = IM1.PORT_CODE
WHERE
    差分 > 0
    AND IM1.KIND_CODE = '110'
    AND IM1.GROUP_CODE = '120'
ORDER BY
    差分 desc,
    港コード desc