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

> Reference material for VAR_SAMP

# VAR_SAMP

Computes the sample variance of all non-`NULL` numeric values produced by an expression. The sample variance measures the average of the squared differences from the sample mean, indicating how spread out the values are within a sample.
For information about the population variance, which measures how spread out the values are within the full population, see [VAR\_POP](/reference-sql/functions-reference/aggregation/variance-pop).

**Alias**: `VARIANCE`

## Syntax

```sql theme={"theme":{"light":"css-variables","dark":"css-variables"}}
{ VARIANCE | VAR_SAMP }(<expression>) [FILTER ([WHERE] <condition>)]
```

## Parameters

| Parameter      | Description                                                                        | Supported input types      |
| :------------- | :--------------------------------------------------------------------------------- | :------------------------- |
| `<expression>` | An expression producing numeric values for which to calculate the sample variance. | `REAL`, `DOUBLE PRECISION` |
| `<condition>`  | An optional boolean expression to filter rows used in aggregation                  | `BOOL`                     |

## Return Type

`VAR_SAMP` returns a result of type `DOUBLE PRECISION`.

### Special cases

* If there is at most one non-`NULL` input value, the result is `NULL`.
* If the input contains an `Inf` or `NaN` value, the result will be `NaN`.

## Example

The following example calculates the sample variance of five grade values:

<div className="query-window">
  ```
  SELECT ROUND(VAR_SAMP(grade::double precision), 3) AS variance
  FROM UNNEST(ARRAY[4.0, 3.7, 3.3, 2.7, 2.7]) AS t(grade);
  ```

  | variance <span>double null</span> |
  | :-------------------------------- |
  | 0.342                             |

  <p><span>Rows: 1</span><span>Execution time: 5.95ms</span></p>
</div>