How many students live in each dorm?
select count ( * ), t3.dorm_name from student as t1 join lives_in as t2 on t1.stuid = t2.stuid join dorm as t3 on t3.dormid = t2.dormid group by t3.dorm_name
What is the average age of the students living in each dorm?
select avg ( t1.age ), t3.dorm_name from student as t1 join lives_in as t2 on t1.stuid = t2.stuid join dorm as t3 on t3.dormid = t2.dormid group by t3.dorm_name