Database: olympics
Question: Among the competitors with age ranges 24 and below, calculate the difference between the number of competitors who weighed greater than 70 kg and competitors who weighted less than 70 kg.
SQL: SELECT COUNT(CASE WHEN T1.weight > 70 THEN 1 ELSE NULL END) - COUNT(CASE WHEN T1.weight < 70 THEN 1 ELSE NULL END) FROM person AS T1 INNER JOIN games_competitor AS T2 ON T1.id = T2.person_id WHERE T2.age < 24