# AVG

> AVG aggregate function in StackQL: the average of the non-NULL values in a column or grouping.

Source: https://stackql.io/language-spec/functions/aggregate/avg

Returns the average value of all non `NULL` values within a column or grouping of columns.  

See also:  
[[` SELECT `]](/language-spec/select)

* * * 

## Syntax

```sql
SELECT AVG(columnExpression) FROM <multipartIdentifier>
[ GROUP BY groupByColumn ];
```

## Arguments

__*columnExpression*__  
A column or expression.

> String and BLOB values which cannot be represented as numeric values are interpreted as `0`.  

> At least one value from the *columnExpression* must be non `NULL` otherwise `NULL` is returned.

__*groupByColumn*__  
A column or columns used to perform summary or aggregate operations against.  The `GROUP BY` clause returns one row for each column grouping.

## Return Value(s)

Returns a floating point value representing the average of the *columnExpression*.

* * *

## Examples

### Return the average of a column expression over an entire resource

```sql
SELECT avg(json_array_length(disks)) as avg_disks
FROM google.compute.instances 
WHERE project = 'stackql-demo' 
AND zone = 'australia-southeast1-a';
```

### Return the average of a column expression grouped by another column expression

```sql
SELECT tags, avg(json_array_length(disks)) as avg_disks
FROM google.compute.instances 
WHERE project = 'stackql-demo' 
AND zone = 'australia-southeast1-a'
GROUP BY json_extract(tags, '$.instanceType');
```

### Use `AVG` as a window function to calculate moving averages

```sql
-- Calculate moving average of commit activity
WITH weekly_totals AS (
    SELECT
        week,
        SUM(json_each.value) as commits_this_week
    FROM github.repos.stats_commit_activity, JSON_EACH(days)
    WHERE owner = 'stackql'
      AND repo = 'stackql'
    GROUP BY week
)
SELECT
    week,
    commits_this_week,
    ROUND(AVG(commits_this_week) OVER (ORDER BY week ROWS BETWEEN 3 PRECEDING AND CURRENT ROW), 1) as four_week_moving_avg
FROM weekly_totals
ORDER BY week;
```

For more information, see [https://www.sqlite.org/lang_aggfunc.html#avg](https://www.sqlite.org/lang_aggfunc.html#avg).