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> Reference material for CUME_DIST window function

# CUME_DIST OVER

Returns the cumulative distribution of the current row within its partition. The result is the number of rows that precede or are peers with the current row, divided by the total number of rows in the partition. Values are always in the range `(0, 1]`.

For more information on usage, please refer to [Window Functions](/reference-sql/functions-reference/window).

## Syntax

```sql theme={"theme":{"light":"css-variables","dark":"css-variables"}}
CUME_DIST() OVER ( [ PARTITION BY <partition_by> ] ORDER BY <order_by> [ASC|DESC] )
```

## Parameters

| Parameter        | Description                                       | Supported input types |
| :--------------- | :------------------------------------------------ | :-------------------- |
| `<partition_by>` | An expression used for the `PARTITION BY` clause. | Any                   |
| `<order_by>`     | An expression used for the `ORDER BY` clause.     | Any                   |

## Return Type

`DOUBLE PRECISION`

## Remarks

* `CUME_DIST` takes no arguments.
* When no `ORDER BY` clause is specified, all rows within the partition are considered peers and `CUME_DIST` returns `1` for every row.
* Unlike `PERCENT_RANK`, the minimum value of `CUME_DIST` is `1/N` (not `0`), where N is the partition size.
* This function respects `NULL` values, and results will be ordered with default null ordering `NULLS LAST` unless otherwise specified in the `ORDER BY` clause.

## Example

The following example ranks each level by `maxpoints` within its `leveltype`, showing what fraction of levels in the same type have a `maxpoints` value less than or equal to the current row:

<div className="query-window">
  ```
  SELECT
      level,
      leveltype,
      maxpoints,
      CUME_DIST() OVER (PARTITION BY leveltype ORDER BY maxpoints) AS cd
  FROM levels
  ORDER BY leveltype, maxpoints;
  ```

  | level <span>int null</span> | leveltype <span>text null</span> | maxpoints <span>int null</span> | cd <span>double</span> |
  | :-------------------------- | :------------------------------- | :------------------------------ | :--------------------- |
  | 6                           | Drift                            | 80                              | 0.5                    |
  | 9                           | Drift                            | 250                             | 1                      |
  | 1                           | FastestLap                       | 20                              | 0.25                   |
  | 3                           | FastestLap                       | 40                              | 0.5                    |
  | 7                           | FastestLap                       | 70                              | 0.75                   |
  | 8                           | FastestLap                       | 100                             | 1                      |
  | 2                           | FirstToComplete                  | 30                              | 0.25                   |
  | 4                           | FirstToComplete                  | 100                             | 0.5                    |
  | 5                           | FirstToComplete                  | 150                             | 0.75                   |
  | 10                          | FirstToComplete                  | 500                             | 1                      |

  <p><span>Rows: 10</span><span>Execution time: 8.19ms</span></p>
</div>