CREATE TABLE student(course VARCHAR(10), mark int, name varchar(10));

INSERT INTO student VALUES 

  ('Maths', 60, 'Thulile'),

  ('Maths', 60, 'Pritha'),

  ('Maths', 70, 'Voitto'),

  ('Maths', 55, 'Chun'),

  ('Biology', 60, 'Bilal'),

   ('Biology', 70, 'Roger');

SET sql_mode = 'ONLY_FULL_GROUP_BY';

SELECT 

  RANK() OVER (PARTITION BY course ORDER BY mark DESC) AS rank, 

  DENSE_RANK() OVER (PARTITION BY course ORDER BY mark DESC) AS dense_rank, 

  ROW_NUMBER() OVER (PARTITION BY course ORDER BY mark DESC) AS row_num, 

  course, mark, name 

FROM student ORDER BY course, mark DESC;