Database: superhero (difficulty: simple)
Question: Which superheroes have a Speed attribute value of less than 50?
SQL: SELECT superhero_name FROM superhero AS T1 WHERE EXISTS (SELECT 1 FROM hero_attribute AS T2 INNER JOIN attribute AS T3 ON T2.attribute_id = T3.id WHERE T3.attribute_name = 'Speed' AND T2.attribute_value < 50 AND T1.id = T2.hero_id)