with t as (
select
user_id,
point
from test_results
where test_id = '100'
),
m as (
select 
avg(point) as m
from t
),
v as (
select
sqrt(avg((point - m) * (point - m)) ) as v
from t, m
)
select 
user_id as USER,
point as PT,
( case when v = 0 then 50
 else 50 + round(10 * (point - m) / v, 1) end) as DEV_VAL
from t, m, v
order by case when v = 0 then 50
 else 50 + round(10 * (point - m) / v, 1) end desc, user_id