SQL in a Nutshell, 2nd Edition

Name

STDDEV_SAMP

Synopsis

Use STDDEV_SAMP to find the sample standard deviation within a group of numeric values.

SQL2003 Syntax

STDDEV_SAMP( numeric_expression )

Oracle

Oracle supports the standard syntax. Oracle also provides the STDDEV function, which operates similar to STDDEV_SAMP except that it returns zero as not NULL when there is only one value in the set.

Oracle also supports analytic syntax:

STDDEV_SAMP (numeric_expression) OVER (window_clause)

For an explanation of the window_clause, see the section later in this chapter titled Section 4.3.

DB2

This platform does not provide a function to compute sample standard deviation.

MySQL

MySQL does not provide a function to compute sample standard deviation. MySQL does provide a function named STDDEV, but it returns the population standard deviation.

PostgreSQL

Use STDDEV.

SQL Server

Use STDEV (with only one D!).

Example

The following example computes the sample standard deviation for the values 1, 2, and 3:

SELECT * FROM test;
         X
----------
         1
         2
         3
SELECT STDDEV_SAMP(x) FROM test;
STDDEV_SAMP(X)
--------------
             1