WITH CAL(CAL_ID,PT_DIFF,PT_VAR) 
AS(SELECT USER_ID,POINT-PT_AVG,POW(POINT-PT_AVG,2)
   FROM TEST_RESULTS,
   (SELECT AVG(POINT) AS PT_AVG
    FROM TEST_RESULTS
    WHERE TEST_ID='100')
   WHERE TEST_ID='100')

SELECT USER_ID AS USER,POINT AS PT,
      (CASE DEV
      	WHEN 0 THEN 50
      	ELSE ROUND(((CAL.PT_DIFF * 10) / DEV) + 50,1)
      END
      )AS DEV_VAL
FROM TEST_RESULTS INNER JOIN CAL ON (CAL_ID = USER),
     (SELECT SQRT(AVG(PT_VAR)) AS DEV
      FROM TEST_RESULTS INNER JOIN CAL ON (CAL_ID = USER_ID)
      WHERE TEST_ID = '100')
WHERE TEST_ID = '100'
ORDER BY DEV_VAL DESC,USER;