Database: pets_1_minus_1_0
Question: What are the students' first names who have both cats and dogs as pets?
SQL: select t1.fname from student_has_pet as t1 join pets as t2 on t1.petid = t2.petid where t2.pettype = 'cat' intersect select t1.fname from student_has_pet as t1 join pets as t2 on t1.petid = t2.petid where t2.pettype = 'dog'