WITH DEV(val) AS 
    (SELECT sqrt(AVG(pw)) FROM (SELECT POW((POINT - AVG(POINT)), 2)AS pw FROM TEST_RESULTS WHERE TEST_ID = '100'))

SELECT
    USER_ID AS USER,
    POINT AS PT,
    (CASE DEV.val
        WHEN 0 THEN 50
        ELSE (SELECT (ROUND((POINT - AVG(POINT)) * 10 / DEV.val + 50 , 1)) FROM TEST_RESULTS CROSS JOIN DEV WHERE TEST_ID = '100')
    END) AS DEV_VAL
FROM
    TEST_RESULTS CROSS JOIN DEV
WHERE
    TEST_RESULTS.TEST_ID = '100'
ORDER BY
    DEV_VAL DESC, USER_ID;