Question: What are the names and ages of every person who is a friend of both Dan and Alice?
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  =  'Alice'