SELECT
     P.PORT_CODE AS '港コード'
    ,P.PORT_NAME AS '港名'
    ,I110.AMT AS '入国者数'
    ,I120.AMT AS '出国者数'
    ,I110.AMT - I120.AMT AS '差分'
FROM
    PORT AS P
INNER JOIN
(
    SELECT
         PORT_CODE
        ,AMT
    FROM
        IMMIGRATION
    WHERE
        GROUP_CODE='120'
    AND KIND_CODE='110'
) AS I110
ON
    I110.PORT_CODE = P.PORT_CODE
INNER JOIN
(
    SELECT
         PORT_CODE
        ,AMT
    FROM
        IMMIGRATION
    WHERE
        GROUP_CODE='120'
    AND KIND_CODE='120'
) AS I120
ON
    I120.PORT_CODE = P.PORT_CODE

WHERE
    I110.AMT > I120.AMT

ORDER BY
     I110.AMT - I120.AMT DESC
    ,P.PORT_CODE DESC