SELECT
    PORT.PORT_CODE AS 港コード,
    PORT.PORT_NAME AS 港名,
    A.AMT AS 入国者数,
    B.AMT AS 出国者数,
    A.AMT - B.AMT AS 差分
FROM
    PORT,IMMIGRATION AS A,IMMIGRATION AS B
WHERE
    PORT.PORT_CODE = A.PORT_CODE AND
    PORT.PORT_CODE = B.PORT_CODE AND
    A.GROUP_CODE = 120 AND
    B.GROUP_CODE = 120 AND
    A.KIND_CODE = 110 AND
    B.KIND_CODE = 120 AND
    B.AMT < A.AMT
ORDER BY 差分 DESC