SELECT
    PORT.PORT_CODE AS '港コード',
    PORT.PORT_NAME AS '港名',
    IMG1.AMT AS '入国者数',
    IMG2.AMT AS '出国者数',
    IMG1.AMT-IMG2.AMT AS '差分'
FROM
    IMMIGRATION AS IMG1
    INNER JOIN IMMIGRATION AS IMG2
        ON IMG2.PORT_CODE = IMG1.PORT_CODE
        AND IMG2.GROUP_CODE = IMG1.GROUP_CODE
        AND IMG2.KIND_CODE = '120'
    INNER JOIN PORT 
        ON PORT.PORT_CODE = IMG1.PORT_CODE
    
WHERE
    IMG1.GROUP_CODE = '120'
    AND IMG1.KIND_CODE = '110'
    AND 差分 > 0
ORDER BY
    差分 DESC,
    IMG1.PORT_CODE DESC;