with tbl1 as(
select 
avg(point) as av
from TEST_RESULTS
where test_id='100'
)

,tbl2 as(
select
power(point-av,2) as pw
from test_results,tbl1
where test_id='100'
)

,tbl3 as(
select
sqrt(avg(pw)) as hensa
from tbl2
)

select 
USER_ID as USER,
POINT as PT,
round((point-tbl1.av)*10/tbl3.hensa,1)+50 as DEV_VAL
from test_results,tbl3,tbl1
where test_id='100'
order by DEV_VAL desc,USER_ID asc