SELECT
    im.PORT_CODE AS 港コード,
    PORT_NAME AS 港名,
    im.AMT AS 入国者数,
    im1.AMT AS 出国者数,
    im.AMT - im1.AMT AS 差分
FROM
    IMMIGRATION AS im
JOIN    IMMIGRATION AS im1
ON      im.PORT_CODE = im1.PORT_CODE
AND     im.KIND_CODE = '110' AND im1.KIND_CODE = '120'
AND     im.GROUP_CODE = im1.GROUP_CODE 
AND     im1.AMT < im.AMT
JOIN    PORT AS po
ON      im.PORT_CODE = po.PORT_CODE
GROUP BY im.PORT_CODE
ORDER BY 5 DESC, 1 DESC