SELECT
    p.PORT_CODE AS 港コード,
    PORT_NAME AS 港名,
    i.IN_AMT AS 入国者数,
    i.OUT_AMT AS 出国者数,
    i.IN_AMT - i.OUT_AMT AS 差分
FROM
    PORT as p
INNER JOIN
   (
        SELECT
            PORT_CODE,
            SUM(CASE WHEN KIND_CODE = "110" THEN AMT ELSE 0 END) AS IN_AMT,
            SUM(CASE WHEN KIND_CODE = "120" THEN AMT ELSE 0 END) AS OUT_AMT
        FROM
            IMMIGRATION as im
        WHERE 
            GROUP_CODE = 120
        GROUP BY
            PORT_CODE
   ) as i
ON
    p.PORT_CODE = i.PORT_CODE
WHERE i.IN_AMT >= i.OUT_AMT
GROUP BY
    p.PORT_CODE
ORDER BY
    差分 DESC, 港コード DESC