VARIANCE [aggregate]

Evaluates the sample variance for each row of the group.

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

VARIANCE ( expression )

Parameters

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

The nonstandard function VARIANCE is provided for compatibility with other databases. It is semantically identical to VAR_SAMP.

This aggregate function differs from analytic function VARIANCE, 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 VARIANCE(household_id) FROM customer_dimension;
     variance
------------------
 74848598.0106764
(1 row)

See also