Table schema:
CREATE TABLE has_pet (stuid VARCHAR, petid VARCHAR); CREATE TABLE student (Fname VARCHAR, stuid VARCHAR); CREATE TABLE pets (petid VARCHAR, pettype VARCHAR)

Question: What are the students' first names who have both cats and dogs as pets?
SQL: SELECT T1.Fname FROM student AS T1 JOIN has_pet AS T2 ON T1.stuid = T2.stuid JOIN pets AS T3 ON T3.petid = T2.petid WHERE T3.pettype = 'cat' INTERSECT SELECT T1.Fname FROM student AS T1 JOIN has_pet AS T2 ON T1.stuid = T2.stuid JOIN pets AS T3 ON T3.petid = T2.petid WHERE T3.pettype = 'dog'