How many students are there in file?
select count(*) from students
What about student addresses?
select count(*) from student_addresses
Show me the line 1 and average montly rentals of those addresses.
select t1.line_1, avg(t2.monthly_rental) from addresses as t1 join student_addresses as t2 on t1.address_id = t2.address_id group by t2.address_id