SELECT
    A.PORT_CODE AS '港コード'
    ,PORT_NAME AS '港名'
    ,B.AMT AS '入国者数'
    ,C.AMT AS '出国者数'
    ,B.AMT - C.AMT AS '差分'
FROM
    PORT A LEFT JOIN
    (SELECT PORT_CODE,AMT FROM IMMIGRATION WHERE KIND_CODE = '110') B ON A.PORT_CODE = B.PORT_CODE LEFT JOIN
    (SELECT PORT_CODE,AMT FROM IMMIGRATION WHERE KIND_CODE = '120') C ON A.PORT_CODE = C.PORT_CODE 
WHERE
    B.AMT - C.AMT > 0
ORDER BY
    B.AMT - C.AMT DESC
    ,A.PORT_CODE DESC