Database schema:

CREATE TABLE city (
	id INTEGER NOT NULL -- example: ['2', '1'],
	city_name TEXT DEFAULT NULL -- example: ['Barcelona', 'London'],
	PRIMARY KEY (id)
)


CREATE TABLE competitor_event (
	event_id INTEGER DEFAULT NULL -- example: ['2', '1'],
	competitor_id INTEGER DEFAULT NULL -- example: ['2', '1'],
	medal_id INTEGER DEFAULT NULL -- example: ['1', '4'],
	CONSTRAINT fk_competitor_event_games_competitor FOREIGN KEY(competitor_id) REFERENCES games_competitor (id),
	CONSTRAINT fk_competitor_event_event FOREIGN KEY(event_id) REFERENCES event (id),
	CONSTRAINT fk_competitor_event_medal FOREIGN KEY(medal_id) REFERENCES medal (id)
)


CREATE TABLE event (
	id INTEGER NOT NULL -- example: ['2', '1'],
	sport_id INTEGER DEFAULT NULL -- example: ['9', '33'],
	event_name TEXT DEFAULT NULL -- example: ["Judo Men's Extra-Lightweight", "Basketball Men's Basketball"],
	PRIMARY KEY (id), 
	CONSTRAINT fk_event_sport FOREIGN KEY(sport_id) REFERENCES sport (id)
)


CREATE TABLE games (
	id INTEGER NOT NULL -- example: ['2', '1'],
	games_year INTEGER DEFAULT NULL -- example: ['2012', '1992'],
	games_name TEXT DEFAULT NULL -- example: ['1992 Summer', '2012 Summer'],
	season TEXT DEFAULT NULL -- example: ['Winter', 'Summer'],
	PRIMARY KEY (id)
)


CREATE TABLE games_city (
	games_id INTEGER DEFAULT NULL -- example: ['2', '1'],
	city_id INTEGER DEFAULT NULL -- example: ['2', '1'],
	CONSTRAINT fk_games_city_city FOREIGN KEY(city_id) REFERENCES city (id),
	CONSTRAINT fk_games_city_games FOREIGN KEY(games_id) REFERENCES games (id)
)


CREATE TABLE games_competitor (
	id INTEGER NOT NULL -- example: ['2', '1'],
	games_id INTEGER DEFAULT NULL -- example: ['2', '1'],
	person_id INTEGER DEFAULT NULL -- example: ['2', '1'],
	age INTEGER DEFAULT NULL -- example: ['23', '24'],
	PRIMARY KEY (id), 
	CONSTRAINT fk_games_competitor_games FOREIGN KEY(games_id) REFERENCES games (id),
	CONSTRAINT fk_games_competitor_person FOREIGN KEY(person_id) REFERENCES person (id)
)


CREATE TABLE medal (
	id INTEGER NOT NULL -- example: ['2', '1'],
	medal_name TEXT DEFAULT NULL -- example: ['Gold', 'Silver'],
	PRIMARY KEY (id)
)


CREATE TABLE noc_region (
	id INTEGER NOT NULL -- example: ['2', '1'],
	noc TEXT DEFAULT NULL -- example: ['AFG', 'AHO'],
	region_name TEXT DEFAULT NULL -- example: ['Afghanistan', 'Netherlands Antilles'],
	PRIMARY KEY (id)
)


CREATE TABLE person (
	id INTEGER NOT NULL -- example: ['2', '1'],
	full_name TEXT DEFAULT NULL -- example: ['A Dijiang', 'A Lamusi'],
	gender TEXT DEFAULT NULL -- example: ['M', 'F'],
	height INTEGER DEFAULT NULL -- example: ['180', '170'],
	weight INTEGER DEFAULT NULL -- example: ['60', '80'],
	PRIMARY KEY (id)
)


CREATE TABLE person_region (
	person_id INTEGER DEFAULT NULL -- example: ['2', '1'],
	region_id INTEGER DEFAULT NULL -- example: ['42', '56'],
	CONSTRAINT fk_person_region_person FOREIGN KEY(person_id) REFERENCES person (id),
	CONSTRAINT fk_person_region_noc_region FOREIGN KEY(region_id) REFERENCES noc_region (id)
)


CREATE TABLE sport (
	id INTEGER NOT NULL -- example: ['2', '1'],
	sport_name TEXT DEFAULT NULL -- example: ['Aeronautics', 'Alpine Skiing'],
	PRIMARY KEY (id)
)

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.
Evidence: SUBTRACT(COUNT(weight > 70), COUNT(weight < 70)) where age < 24;

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