Database: pets_1_minus_1_0
Question: Find the first name and age of students who have a dog but do not have a cat as a pet.
SQL: select t1.fname , t1.age from student_has_pet as t1 join pets as t2 on t1.petid = t2.petid where t2.pettype = 'dog' and t1.stuid not in ( select t1.stuid from student_has_pet as t1 join pets as t2 on t1.petid = t2.petid where t2.pettype = 'cat' )