VAR_SAMP [Aggregate]

Evaluates the sample variance for each row of the group. This is defined as the sum of squares of the difference of expression from the mean of expression divided by the number of remaining rows minus 1:

(SUM(expression*expression) - SUM(expression) *SUM(expression) / COUNT(expression)) / (COUNT(expression) -1)

Behavior Type

Immutable

Syntax

VAR_SAMP ( expression )

Parameters

expression

Any NUMERIC data type or any non-numeric data type that can be implicitly converted to a numeric data type. VAR_SAMP returns the same data type as expression.

Related Functions

VAR_SAMP is semantically identical to nonstandard function VARIANCE, which is provided for compatibility with other databases.
This aggregate function differs from analytic function VAR_SAMP, which computes the sample variance of the current row with respect to the group of rows within a window.

Examples

The following example returns the sample variance for each household ID in the customer table.

=> SELECT VAR_SAMP(household_id) FROM customer_dimension;
     var_samp     
------------------
 74848598.0106764
(1 row)