Table schema:
CREATE TABLE Person (name VARCHAR, age INTEGER); CREATE TABLE PersonFriend (name VARCHAR, friend VARCHAR); CREATE TABLE Person (name VARCHAR)

Question: Find the name of the person who has friends with age above 40 and under age 30?
SQL: SELECT T1.name FROM Person AS T1 JOIN PersonFriend AS T2 ON T1.name = T2.name WHERE T2.friend IN (SELECT name FROM Person WHERE age > 40) INTERSECT SELECT T1.name FROM Person AS T1 JOIN PersonFriend AS T2 ON T1.name = T2.name WHERE T2.friend IN (SELECT name FROM Person WHERE age < 30)