WITH T AS (
    SELECT *
    FROM TEST_RESULTS
    WHERE TEST_ID = '100'
),
AVG_TABLE AS (
    SELECT AVG(POINT) AS AVERAGE FROM T
),
SD AS (
    SELECT SQRT(AVG((POINT - AVERAGE) * (POINT - AVERAGE))) AS SD
    FROM T CROSS JOIN AVG_TABLE
)

SELECT USER_ID AS USER, POINT AS PT,
    CASE
        WHEN SD <> 0 THEN ROUND((1.0 * POINT - AVERAGE) * 10 / SD + 50, 1)
        ELSE 50
    END AS DEV_VAL
FROM T CROSS JOIN AVG_TABLE CROSS JOIN SD
ORDER BY DEV_VAL DESC, USER_ID