STDDEV function [Aggregate]

Returns the standard deviation of a set of numbers.

STDDEV ( [ ALL ] expression )

Given this data:

SELECT Salary FROM Employees WHERE DepartmentID = 300

The following statement returns the value 32617.8446712838471:

SELECT STDDEV ( Salary ) FROM Employees
WHERE DepartmentID = 300

Given this data:

SELECT UnitPrice FROM Products WHERE Name = 'Tee Shirt'

The following statement returns the value 2.88675134594813049:

SELECT STDDEV ( UnitPrice ) FROM Products
WHERE Name = 'Tee Shirt'

The formula used to calculate STDDEV is:

STDDEV returns a result of data type DOUBLE precision floating-point. If applied to the empty set, the result is NULL, which returns NULL for a one-element input set.

STDDEV does not support the keyword DISTINCT. A syntax error is returned if you use DISTINCT with STDDEV.