WITH AVE AS(
SELECT
	AVG(POINT) AS AV
FROM
	TEST_RESULTS
WHERE
	TEST_ID = '100'
)
,TB AS (SELECT
    CASE SQRT(AVG((POINT - AV) * (POINT - AV))) 
        WHEN 0 THEN 50
        ELSE SQRT(AVG((POINT - AV) * (POINT - AV))) 
    END AS AA
FROM
    TEST_RESULTS, AVE
WHERE
	TEST_ID = '100')
	
SELECT
    USER_ID AS USER
    ,POINT AS PT
    ,ROUND((POINT - AV) * 10 / TB.AA + 50, 1) AS DEV_VAL
FROM
    TEST_RESULTS, AVE, TB
WHERE
	TEST_ID = '100'
ORDER BY
    DEV_VAL DESC, USER_ID