MySQL 8.0

By using db<>fiddle, you agree to license everything you submit by Creative Commons CC0.

CREATE TABLE tournaments (
  `id` VARCHAR(12),
  `game` VARCHAR(12)
);

INSERT INTO tournaments
  (`id`, `game`)
VALUES
  ('1'    ,'EXAMPLE'),
  ('2'    ,'TETRIS'),
  ('3'    ,'MARIO');

CREATE TABLE matches (
  `id` int,
  `tournament_id` int,
  `date_start` datetime,
  `date_finished` datetime
);

INSERT INTO matches
  (`id`, `tournament_id`, `date_start`, `date_finished`)
VALUES
  ('1'         ,'1'         ,'2024-01-18 01:10:00'   ,'2024-01-18 01:12:00'),
  ('2'          ,'2'         ,'2024-01-18 01:10:00'   ,'2024-01-18 01:18:00'),
  ('3'          ,'3'         ,'2024-01-18 01:10:00'   ,'2024-01-18 01:16:00'),
  ('4'          ,'3'         ,'2024-01-18 01:10:00'   ,'2024-01-18 01:22:00'),
  ('5'          ,'2'         ,'2024-01-18 01:10:00'   ,'2024-01-18 01:31:00'),
  ('6'          ,'1'         ,'2024-01-18 01:10:00'   ,'2024-01-18 01:19:00'),
  ('7'          ,'2'         ,'2024-01-18 01:10:00'   ,'2024-01-18 01:45:00'),
  ('8'          ,'3'         ,'2024-01-18 01:10:00'   ,'2024-01-18 01:28:00'),
  ('9'          ,'3'         ,'2024-01-18 01:10:00'   ,'2024-01-18 01:54:00');

Records: 3  Duplicates: 0  Warnings: 0

Records: 9  Duplicates: 0  Warnings: 0

tournament_id	game	median
1	EXAMPLE	5.5000
2	TETRIS	21.0000
3	MARIO	15.0000