Hi, can I see the list of customers?
select * from customers
What customers have a policy?
select * from policies as t1 join customers as t2 on t1.customer_id = t2.customer_id
What customers don't have a policy?
select * from customers except select * from policies as t1 join customers as t2 on t1.customer_id = t2.customer_id
When did the policy holders get their policy?
select start_date from policies