tj11:

select sex,count(sex)
from t_athletes
group by sex;

tj12:

select name 姓名,TIMESTAMPDIFF(year,birthday,'2024-1-1') 年龄
from t_athletes

tj13:

SELECT * 
FROM 
t_athletes
 WHERE 
	id 
	NOT IN (
    SELECT 
		aid 
	FROM 
		t_match 
	WHERE 
		sid 
        IN (SELECT id FROM t_sport WHERE name like '%跑步'));

tj14:

select t_sport.name ,t_athletes.name,t_athletes.sex,t_athletes.birthday
from  t_athletes join t_match on t_athletes.id=t_match.aid
join t_sport on t_match.sid=t_sport.id
where t_match.grade='第一名'