stddev_pop
Returns the population standard deviation (square root of variance) of non-NULL values.
See also STDDEV_SAMP, which returns the sample standard deviation (square root of variance).
Syntax
Section titled “Syntax”stddev_pop( <expr>)Arguments
Section titled “Arguments”<expr>
Section titled “<expr>”An expression that evaluates to a numeric value. This is the expression on which the standard deviation is calculated.
Returns
Section titled “Returns”The data type of the returned value is float.
If all records inside a group are NULL, this function returns NULL.