# Source: https://docs.oxla.com/sql-reference/sql-functions/aggregate-functions/ordered-set-aggregate-functions/percentile-cont.md

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# PERCENTILE_CONT()

## Overview

`PERCENTILE_CONT()` is an ordered-set aggregate function used to compute continuous percentiles from a set of values. The **continuous percentile** returns an interpolated value based on the distribution of the input data, while **multiple continuous percentiles** return an array of results matching the shape of the `fractions` parameter with each non-null element replaced by the value corresponding to that percentile.

<div>
  <h2>Syntax</h2>
  <p> The syntax for this function is as follows:</p>

  <Tabs>
    <Tab title="Continuous Percentile" onClick={() => handleTabChange('tab1')}>
      <div>
        <code>
          ```sql  theme={null}
          PERCENTILE_CONT(fraction) WITHIN GROUP (ORDER BY order_list)
          ```
        </code>

        <Note> This function is often used in conjunction with the `WITHIN GROUP` clause to specify how to order the data before calculating the percentile.</Note>
        <h2>Parameters </h2>
        <p>- `fraction`: decimal value between 0 and 1 representing the desired percentile (e.g. 0.25 for the 25th percentile)</p>
      </div>
    </Tab>

    <Tab title="Multiple Continuous Percentile" onClick={() => handleTabChange('tab2')}>
      <div>
        <code>
          ```sql  theme={null}
          PERCENTILE_CONT(fractions) WITHIN GROUP (ORDER BY order_list)
          ```
        </code>

        <Note> This function is often used in conjunction with the `WITHIN GROUP` clause to specify how to order the data before calculating the percentile.</Note>
        <h2>Parameters</h2>
        <p>- `fractions`: array of decimal values between 0 and 1 representing the desired percentiles (e.g. `ARRAY[0.25, 0.50, 0.75, 0.90]`)</p>
      </div>
    </Tab>
  </Tabs>
</div>

## Example

For the needs of this section we will use a simplified version of the `film` table from the
<a href="https://www.postgresql.org/ftp/projects/pgFoundry/dbsamples/pagila/pagila/" target="_blank">Pagila database</a>, that will contain only the `title`, `length` and `rating` columns.

```sql  theme={null}
DROP TABLE IF EXISTS film;
CREATE TABLE film (
  title text NOT NULL,
  length int,
  rating text
);
INSERT INTO film(title, length, rating) VALUES
  ('ATTRACTION NEWTON', 83, 'PG-13'),
  ('CHRISTMAS MOONSHINE', 150, 'NC-17'),
  ('DANGEROUS UPTOWN', 121, 'PG'),
  ('KILL BROTHERHOOD', 54, 'G'),
  ('HALLOWEEN NUTS', 47, 'PG-13'),
  ('HOURS RAGE', 122, 'NC-17'),
  ('PIANIST OUTFIELD', 136, 'NC-17'),
  ('PICKUP DRIVING', 77, 'G'),
  ('INDEPENDENCE HOTEL', 157, 'NC-17'),
  ('PRIVATE DROP', 106, 'PG'),
  ('SAINTS BRIDE', 125, 'G'),
  ('FOREVER CANDIDATE', 131, 'NC-17'),
  ('MILLION ACE', 142, 'PG-13'),
  ('SLEEPY JAPANESE', 137, 'PG'),
  ('WRATH MILE', 176, 'NC-17'),
  ('YOUTH KICK', 179, 'NC-17'),
  ('CLOCKWORK PARADISE', 143, 'PG-13');
```

This query calculates the median film length within each rating category.

```SQL  theme={null}
SELECT rating, PERCENTILE_CONT(0.50) WITHIN GROUP (ORDER BY length) AS "50th percentile" FROM film
GROUP BY rating; 
```

By executing the code above we will get the following output:

```sql  theme={null}
 rating | 25th percentile 
--------+-----------------
 PG-13  |              74
 PG     |           113.5
 NC-17  |           133.5
 G      |            65.5
(4 rows)
```