that's true, but SQL Server and MC Access both support it.
Also, it is in the SQL standards. It doesn't matter how the Foxpro engine calculates it.

Also, I wrote a UDF to calculate STDDEV in a single pass -
(why I don't use it - it doesn't work with GROUP BY)
here's how:
It depends on PUBLIC variables to remember all average, count, sum and all the reqd. variables used to calculate STD. DEV.
It recalculates STD DEV while the SQL Statement is passing through each record.
The last value is what the SQL statement returns.