> ## Documentation Index
> Fetch the complete documentation index at: https://docs.oxla.com/llms.txt
> Use this file to discover all available pages before exploring further.

# VARIANCE()

## Overview

The `VARIANCE()` aggregate function calculate the sample variance of a set of numeric values. Variance measures the spread of data points around the mean, providing insight into how much the values deviate from the average.

## Syntax

The syntax for this function is as follows:

```sql theme={null}
VARIANCE(expression)
```

## Parameters

* `expression`: numeric expression or column for which the variance is calculated

## Example

For the needs of this section, we're going to use a simplified version of the `film` table from the Pagila database, containing only the `title`, `length` and `rating` columns. The complete schema for the `film` table can be found on the
<a href="https://www.postgresql.org/ftp/projects/pgFoundry/dbsamples/pagila/pagila/" target="_blank">Pagila</a> database website.

```sql theme={null}
DROP TABLE IF EXISTS film;
CREATE TABLE film (
  title text NOT NULL,
  length int,
  rating int
);
INSERT INTO film(title, length, rating) VALUES
  ('ATTRACTION NEWTON', 83, 5),
  ('CHRISTMAS MOONSHINE', 150, 7),
  ('DANGEROUS UPTOWN', 121, 4),
  ('KILL BROTHERHOOD', 54, 3),
  ('HALLOWEEN NUTS', 47, 5),
  ('HOURS RAGE', 122, 7),
  ('PIANIST OUTFIELD', 136, 7),
  ('PICKUP DRIVING', 77, 3),
  ('INDEPENDENCE HOTEL', 157, 7),
  ('PRIVATE DROP', 106, 4),
  ('SAINTS BRIDE', 125, 3),
  ('FOREVER CANDIDATE', 131, 7),
  ('MILLION ACE', 142, 5),
  ('SLEEPY JAPANESE', 137, 4),
  ('WRATH MILE', 176, 7),
  ('YOUTH KICK', 179, 7),
  ('CLOCKWORK PARADISE', 143, 5);
```

The query below uses the `VARIANCE()` function to calculate the variance for the `length` column:

```sql theme={null}
SELECT
    VARIANCE(length) AS LengthVariance
FROM film;
```

By executing the code above, we will get the following output:

```sql theme={null}
   lengthvariance   
--------------------
 1473.0955882352937
(1 row)
```