SELECT
    P.PORT_CODE
    , P.PORT_NAME
    , (CASE WHEN KIND_CODE = "110" THEN IM.AMT ELSE 0 END) AS IN_AMT
    , (CASE WHEN KIND_CODE = "120" THEN IM.AMT ELSE 0 END) AS OUT_AMT
    , (CASE WHEN KIND_CODE = "110" THEN IM.AMT ELSE 0 END) - (CASE WHEN KIND_CODE = "120" THEN IM.AMT ELSE 0 END) AS DIFF
FROM
    PORT AS P
    INNER JOIN IMMIGRATION AS IM 
        ON P.PORT_CODE = IM.PORT_CODE 
    INNER JOIN GRP AS GP 
        ON GP.GROUP_CODE = IM.GROUP_CODE
        AND GP.GROUP_CODE = "120"
WHERE IN_AMT > OUT_AMT
ORDER BY
    DIFF DESC
    , P.PORT_CODE DESC;