aggregate

VARIANCE()

Returns the variance (squared spread) of a set of numeric values.

Description

VARIANCE is an aggregate function that measures how far a set of numbers spreads from their mean, squared. It's the square of the standard deviation and is widely used in statistics. A larger variance means the values are more dispersed.

Syntax

VARIANCE(expression)
VAR_SAMP(expression)
VAR_POP(expression)

Parameters

Name	Description	Optional
expression	A numeric column or expression.	No

Return Type

Returns a DOUBLE. With fewer than two non-NULL values it typically returns NULL.

Examples

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Variance vs STDDEV

STDDEV is just the square root of VARIANCE. Use variance when you need the squared unit, or standard deviation for an interpretable, same-unit measure.

Common Mistakes

Mixing sample and population. VAR_SAMP vs VAR_POP differ slightly; VARIANCE usually means the sample form.
Interpreting the unit. Variance is in squared units, which can be hard to reason about. Prefer STDDEV for readability.
Non-numeric input. Variance requires numbers; text columns will error.