stddev_samp
Returns the sample standard deviation (square root of sample variance) of non-NULL values.
See also STDDEV_POP, which returns the population standard deviation (square root of variance).
Syntax
Section titled “Syntax”stddev_samp ( <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.