with t1 as (select * from TEST_RESULTS where TEST_ID='100'),
t2 as (select avg(point) as avg from t1),
t3 as (select t1.*, t2.avg from t1,t2),
t4 as (select sqrt(sum(t3.point * t3.point - t3.avg * t3.avg) / count(1)) as std from t3)
select 
t3.user_id as USER
,t3.point as PT

, CASE 
    when t4.std = 0 then 50
    else round((t3.point - t3.avg ) * 10 / t4.std + 50,1)
end as DEV_VAL
from t3,t4
order by 3 desc, 1