18.0400 |        20.1693 |   325.4400 |
+----------+---------------+----------------+------------+

As a window function:

CREATE OR REPLACE TABLE student_test (name CHAR(10), test CHAR(10), score
TINYINT);

INSERT INTO student_test VALUES 
  ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73),
  ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31),
  ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88),
  ('Tatiana', 'SQL', 87);

SELECT name, test, score, VAR_POP(score) 
 OVER (PARTITION BY test) AS variance_results FROM student_test;
+---------+--------+-------+------------------+
| name    | test   | score | variance_results |
+---------+--------+-------+------------------+
| Chun    | SQL    |    75 |         287.1875 |
| Esben   | SQL    |    43 |         287.1875 |
| Kaolin  | SQL    |    56 |         287.1875 |
| Tatiana | SQL    |    87 |         287.1875 |
| Chun    | Tuning |    73 |         582.0000 |
| Esben   | Tuning |    31 |         582.0000 |
| Kaolin  | Tuning |    88 |         582.0000 |
+---------+--------+-------+------------------+

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