Question: Find the name and age of the person who is a friend of both Dan and Zach
SQL: SELECT T1.name ,  T1.age FROM Person AS T1 JOIN PersonFriend AS T2 ON T1.name   =   T2.name WHERE T2.friend   =   'Dan' INTERSECT SELECT T1.name ,   T1.age FROM Person AS T1 JOIN PersonFriend AS T2 ON T1.name   =   T2.name WHERE T2.friend   =   'Zach'