The PERCENTILE_DISC() window function was first introduced
with in MariaDB 10.3.3.
 
Syntax
------ 

Description
----------- 
PERCENTILE_DISC() (standing for discrete percentile) is a
window function which returns the first value in the set
whose ordered position is the same or more than the
specified fraction.
 
Essentially, the following process is followed to find the
value to return:
Get the number of rows in the partition.
Walk through the partition, in order, until finding the the
first row with CUME_DIST() > function_argument.
 
Examples
-------- 
CREATE TABLE book_rating (name CHAR(30), star_rating
TINYINT);
 
INSERT INTO book_rating VALUES ('Lord of the Ladybirds',
5);
INSERT INTO book_rating VALUES ('Lord of the Ladybirds',
3);
INSERT INTO book_rating VALUES ('Lady of the Flies', 1);
INSERT INTO book_rating VALUES ('Lady of the Flies', 2);
INSERT INTO book_rating VALUES ('Lady of the Flies', 5);
 
SELECT name, PERCENTILE_DISC(0.5) WITHIN GROUP (ORDER BY
star_rating)
 OVER (PARTITION BY name) AS pc FROM book_rating;
 
+-----------------------+------+
| name | pc |
+-----------------------+------+
| Lord of the Ladybirds | 3 |
| Lord of the Ladybirds | 3 |
| Lady of the Flies | 2 |
| Lady of the Flies | 2 |
| Lady of the Flies | 2 |
+-----------------------+------+
5 rows in set (0.000 sec)
 
SELECT name, PERCENTILE_DISC(0) WITHIN GROUP (ORDER BY
star_rating) 
 OVER (PARTITION BY name) AS pc FROM book_rating;
 
+-----------------------+------+
| name | pc |
+-----------------------+------+
| Lord of the Ladybirds | 3 |
| Lord of the Ladybirds | 3 |
| Lady of the Flies | 1 |
| Lady of the Flies | 1 |
| Lady of the Flies | 1 |
+-----------------------+------+
5 rows in set (0.000 sec)
 
SELECT name, PERCENTILE_DISC(1) WITHIN GROUP (ORDER BY
star_rating) 
 OVER (PARTITION BY name) AS pc FROM book_rating;
 
+-----------------------+------+
| name | pc |
+-----------------------+------+
| Lord of the Ladybirds | 5 |
| Lord of the Ladybirds | 5 |
| Lady of the Flies | 5 |
| Lady of the Flies | 5 |
| Lady of the Flies | 5 |
+-----------------------+------+
5 rows in set (0.000 sec)
 
SELECT name, PERCENTILE_DISC(0.6) WITHIN GROUP (ORDER BY
star_rating) 
 OVER (PARTITION BY name) AS pc FROM book_rating;
 
+-----------------------+------+
| name | pc |
+-----------------------+------+
| Lord of the Ladybirds | 5 |
| Lord of the Ladybirds | 5 |
| Lady of the Flies | 2 |
| Lady of the Flies | 2 |
| Lady of the Flies | 2 |
+-----------------------+------
 


URL: https://mariadb.com/kb/en/percentile_disc/