The stddevw_samp function returns the weighted standard deviation of the sample for a set of values.
The syntax of the stddevw_samp function is
x are the values for which the standard deviation of the sample
shall be calculated.
Null values are ignored.
If the number of values is zero, the function returns null.
w are the weights. If no value is provided the weight is assumed to be 1.
SELECT country, stddevw_samp(price) FROM sales GROUP BY country;