WITH
AVG_SCORE AS (
    SELECT AVG(POINT) AS AVG_SCORE
    FROM TEST_RESULTS
    WHERE TEST_ID = '100'
)
, STDEV AS (
    SELECT SQRT(AVG((POINT - (SELECT AVG_SCORE FROM AVG_SCORE))*(POINT - (SELECT AVG_SCORE FROM AVG_SCORE)))) AS STDEV
    FROM TEST_RESULTS
    WHERE TEST_ID = '100'
)
SELECT
    USER_ID AS USER
    ,POINT AS PT
    ,50 + (POINT - AVG_SCORE.AVG_SCORE)*10/STDEV AS DEV_VAL
FROM TEST_RESULTS
CORSS JOIN STDEV
CORSS JOIN AVG_SCORE