What are all the different employee address details?
select distinct address_details from addresses as t1 join employees as t2 on t1.address_id = t2.employee_address_id
At which adresses do no employees live?
select * from addresses where address_id not in (select employee_address_id from employees)
What states or provinces are they in?
select state_province_county from addresses where address_id not in (select employee_address_id from employees)