WITH D AS (
SELECT
USER_ID,
POINT
FROM TEST_RESULTS
WHERE TEST_ID = '100'
), mean AS (
SELECT
AVG(POINT) AS avg
FROM D
), std AS (
SELECT
SQRT(AVG((POINT - avg) * (POINT - avg))) AS SD
FROM D
CROSS JOIN mean
)

SELECT
    USER_ID USER,
    POINT PT,
    CASE
      WHEN SD = 0 THEN 50
      ELSE ROUND(1.0 * (POINT - avg) * 10 / SD + 50, 1)
    END DEV_VAL
FROM D
CROSS JOIN mean
CROSS JOIN std

ORDER BY 
DEV_VAL DESC,
USER