CREATE TABLE people (people_id NUMBER, name CLOB, age NUMBER, height NUMBER, hometown CLOB)
CREATE TABLE gymnast (gymnast_id NUMBER, floor_exercise_points NUMBER, pommel_horse_points NUMBER, rings_points NUMBER, vault_points NUMBER, parallel_bars_points NUMBER, horizontal_bar_points NUMBER, total_points NUMBER)

From which hometowns did both people older than 23 and younger than 20 come from?
SELECT hometown FROM people WHERE age > 23 INTERSECT SELECT hometown FROM people WHERE age < 20
SELECT "hometown" FROM "people" WHERE "age" > 23 INTERSECT SELECT "hometown" FROM "people" WHERE "age" < 20