> For the complete documentation index, see [llms.txt](https://upsolver.gitbook.io/content/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://upsolver.gitbook.io/content/reference-1/functions-and-operators/functions/aggregate/approx_count_distinct.md).

# APPROX\_COUNT\_DISTINCT

Approximates the number of distinct non-null input values. 

This function is used as an approximation of [`COUNT(DISTINCT ...)`](/content/reference-1/functions-and-operators/functions/aggregate/count-distinct-....md) in order to improve performance. It should be used when there are relatively few (under one million) rows, and where the total number of distinct values is high.

## Syntax

```sql
APPROX_COUNT_DISTINCT(X)
```

## Arguments

#### `X`

Type: any type

The values to be counted.

## Returns

Type: `bigint`

Returns the approximate number of distinct non-null input values. 

If all input values are null, zero is returned.

***

## Examples

### Transformation job example

#### SQL

{% code overflow="wrap" %}

```sql
CREATE JOB function_operator_example
    ADD_MISSING_COLUMNS = TRUE
AS INSERT INTO default_glue_catalog.upsolver_samples.orders_transformed_data
    MAP_COLUMNS_BY_NAME
    SELECT 
        LOWER(ordertype) AS ordertype,
        ROUND(AVG(nettotal), 2) AS avgtotal
    FROM default_glue_catalog.upsolver_samples.orders_raw_data 
    WHERE $commit_time BETWEEN run_start_time() - PARSE_DURATION('1d') 
        AND run_end_time()
    GROUP BY 1
    LIMIT 2;
```

{% endcode %}

#### Query result

| ordertype | avgtotal |
| --------- | -------- |
| pickup    | 1062.14  |
| shipping  | 1061.91  |


---

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