Hi Mario, me again.. ;)

i found out another equivalent STDDEV calculation expression
can calculates result by single pass the rows.
(i hope so, if FB doesn't have an interpret problem...)

sqrt( N*sigma(x*x) - sigma(x)*sigma(x) ) / N

select
sqrt( count(x) * sum(x*x) - sum(x)*sum(x) ) / count(x) as DEVOFX
from mytable
where mydate>?


Regards.

Ali