> This page location: Window Functions > CUME_DIST
> Full Neon documentation index: https://neon.com/docs/llms.txt

# PostgreSQL CUME_DIST Function

**Info:** The CUME_DIST() function works the same way across every PostgreSQL deployment, so you can apply what you learn here to Postgres anywhere you run it. If you're an enterprise looking for managed Postgres built for the AI era, [Lakebase](https://www.databricks.com/product/lakebase) delivers the performance, security, and native Lakehouse integration your teams need. If you're a developer or startup who needs to ship and scale fast, [Neon](https://neon.com) is the Postgres platform built for you.

**Summary**: in this tutorial, you will learn how to use the PostgreSQL `CUME_DIST()` function to calculate the cumulative distribution of a value within a set of values.

## PostgreSQL CUME_DIST() function overview

Sometimes, you may want to create a report that shows the top or bottom x% values from a data set, for example, top 1% of products by revenue. Fortunately, PostgreSQL provides us with the `CUME_DIST()` function to calculate it.

The `CUME_DIST()` function returns the cumulative distribution of a value within a set of values. In other words, it returns the relative position of a value in a set of values.

The syntax of the `CUME_DIST()` function is as follows:

```sql
 CUME_DIST() OVER (
    [PARTITION BY partition_expression, ... ]
    ORDER BY sort_expression [ASC | DESC], ...
)

```

Let's examine this syntax in detail.

### PARTITION BY clause

The `PARTITION BY` clause divides rows into multiple partitions to which the function is applied.

The `PARTITION BY` clause is optional. If you skip it, the `CUME_DIST()` function will treat the whole result set as a single partition.

### ORDER BY clause

The `ORDER BY` clause sorts rows in each partition to which the `CUME_DIST()` function is applied.

### Return value

The `CUME_DIST()` a double precision value which is greater than 0 and less than or equal to 1:

```sql
0 < CUME_DIST() <= 1

```

The function returns the same cumulative distribution values for the same tie values.

## PostgreSQL CUME_DIST() examples

First, [create a new table](../postgresql-tutorial/postgresql-create-table) named `sales_stats` that stores the  sales revenue by employees:

```sql
CREATE TABLE sales_stats(
    name VARCHAR(100) NOT NULL,
    year SMALLINT NOT NULL CHECK (year > 0),
    amount DECIMAL(10,2) CHECK (amount >= 0),
    PRIMARY KEY (name,year)
);

```

Second, [insert](../postgresql-tutorial/postgresql-insert) some rows into the `sales_stats` table:

```sql
INSERT INTO
    sales_stats(name, year, amount)
VALUES
    ('John Doe',2018,120000),
    ('Jane Doe',2018,110000),
    ('Jack Daniel',2018,150000),
    ('Yin Yang',2018,30000),
    ('Stephane Heady',2018,200000),
    ('John Doe',2019,150000),
    ('Jane Doe',2019,130000),
    ('Jack Daniel',2019,180000),
    ('Yin Yang',2019,25000),
    ('Stephane Heady',2019,270000);

```

The following examples help you get a better understanding of the `CUME_DIST()` function.

### 1) Using PostgreSQL CUME_DIST() function over a result set example

The following example returns the sales amount percentile for each sales employee in 2018:

```sql
SELECT
    name,
    year,
    amount,
    CUME_DIST() OVER (
        ORDER BY amount
    )
FROM
    sales_stats
WHERE
    year = 2018;

```

Here is the output:

![PostgreSQL CUME\_DIST Function over a result set example](https://neon.com/postgresqltutorial/PostgreSQL-CUME_DIST-Function-over-a-result-set-example.png)As clearly shown in the output, we can find that 80% of sales employees have sales less than or equal to 150K in 2018.

### 2) Using PostgreSQL CUME_DIST() function over a partition example

The following example uses the `CUME_DIST()` function to calculate the sales percentile for each sales employee in 2018 and 2019.

```sql
SELECT
    name,
	year,
	amount,
    CUME_DIST() OVER (
		PARTITION BY year
        ORDER BY amount
    )
FROM
    sales_stats;

```

Here is the output:

![PostgreSQL CUME\_DIST Function over a partition example](https://neon.com/postgresqltutorial/PostgreSQL-CUME_DIST-Function-over-a-partition-example.png)
In this example:

- The `PARTITION BY`clause divided the rows into two partitions by the year 2018 and 2019.
- The `ORDER BY` clause sorted sales amount of every employee in each partition from high to low to which the `CUME_DIST()` function is applied.

In this tutorial, you have learned how to use the PostgreSQL `CUME_DIST()` function to calculate the cumulative distribution of a value in a group of values.

---

## Related docs (Window Functions)

- [DENSE_RANK](https://neon.com/postgresql/window-function/dense_rank-function)
- [FIRST_VALUE](https://neon.com/postgresql/window-function/first_value-function)
- [LAG](https://neon.com/postgresql/window-function/lag-function)
- [LAST_VALUE](https://neon.com/postgresql/window-function/last_value-function)
- [LEAD](https://neon.com/postgresql/window-function/lead-function)
- [NTH_VALUE](https://neon.com/postgresql/window-function/nth_value-function)
- [NTILE](https://neon.com/postgresql/window-function/ntile-function)
- [PERCENT_RANK](https://neon.com/postgresql/window-function/percent_rank-function)
- [RANK](https://neon.com/postgresql/window-function/rank-function)
- [ROW_NUMBER](https://neon.com/postgresql/window-function/row_number)