SQL in a Nutshell, 3rd Edition

Name

VAR_SAMP

Use VAR_SAMP to compute the sample variance of a set of values.

ANSI SQL Standard Syntax

VAR_SAMP(numeric_expression)

MySQL and PostgreSQL

MySQL and PostgreSQL support the ANSI SQL syntax.

Oracle

Oracle supports the standard syntax. You may alternatively use the VARIANCE function, which differs from VAR_SAMP by returning zero (instead of NULL) for sets that contain only a single value.

Oracle also supports the following analytic syntax:

VAR_SAMP(numeric_expression) OVER (window_clause)

For an explanation of the window_clause, see the section later in this chapter titled “ANSI SQL Window Functions.”

SQL Server

Use the VAR function.

Example

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

SELECT * FROM test;
         X
----------
         1
         2
         3

SELECT VAR_SAMP(x) FROM test;
VAR_SAMP(X)
-----------
          1