WITH ST1 AS (
    SELECT
        USER_ID
        ,POINT
        ,AVE_POINT
        ,POINT - AVE_POINT AS DIFF
        ,(POINT - AVE_POINT) * (POINT - AVE_POINT) AS VA
    FROM TEST_RESULTS
    CROSS JOIN (
        SELECT
            AVG(POINT) AS AVE_POINT
        FROM TEST_RESULTS
    )
    WHERE TEST_ID = '100'
)
SELECT
    USER_ID AS USER
    ,POINT AS PT
    ,CASE 
        WHEN TEST_SD != 0 THEN 
            ROUND(((POINT - AVE_POINT) * 10 / TEST_SD) + 50, 1)
        ELSE 50
    END AS DEV_VAL
FROM ST1
CROSS JOIN (
    SELECT
        SQRT(AVG(VA)) AS TEST_SD
    FROM ST1
)
ORDER BY
    DEV_VAL DESC,
    USER_ID;