How many customers have addresses on file?
select count(distinct customer_id) from customer_addresses as t1 join addresses as t2 on t1.address_id = t2.address_id
What different states are they from?
select distinct state_province_county from addresses
Show all information for customers living in the state of California.
select * from customers as t1 join customer_addresses as t2 on t1.customer_id = t2.customer_id join addresses as t3 on t2.address_id = t3.address_id where t3.state_province_county = 'California'
Show the names of all customers except these.
select customer_name from customers except select t1.customer_name from customers as t1 join customer_addresses as t2 on t1.customer_id = t2.customer_id join addresses as t3 on t2.address_id = t3.address_id where t3.state_province_county = 'California'