This query:
SELECT
rank() over (ORDER BY max(fs_score) desc) AS nr,
nome_e_cognome AS "Player Name", max(fs_score) AS "Best score"
FROM scheda_atleta
INNER JOIN at on at.id=scheda_atleta.atleta
Group BY at.id, nome_e_cognome;```
produces:
<pre>
+----+----------------+------------+
| nr | Player Name | Best score|
+----+----------------+------------+
| 1 | Jerry | 14.32 |
| 2 | Tom Tom | 11.25 |
+----+----------------+------------+</pre>
select
queries in Joomla here: docs.joomla.org/Selecting_data_using_JDatabase