WITH table1 AS(
SELECT 
USER_ID,TEST_ID,POINT, 
  (SELECT AVG(POINT) FROM TEST_RESULTS) AS avg_point 
FROM TEST_RESULTS
WHERE TEST_ID = "100"
),

table2 AS(
SELECT
    *
    ,POWER((POINT - avg_point), 2) AS power_1
FROM table1
)
,
table3 AS (
SELECT
    *
    ,SQRT((SELECT AVG(power_1) FROM TEST_RESULTS)) AS avg_point_2 
FROM table2
)

SELECT
    USER_ID AS USER
    ,POINT AS PT
    ,((POINT-avg_point)*10)/avg_point_2 + 50 AS DEV_VAL
FROM table3;