Show the first name and last name for all customers.
select customer_first_name, customer_last_name from customers
Also show the number of accounts owned by each of them.
select t2.customer_first_name, t2.customer_last_name, count(*) from accounts as t1 join customers as t2 on t1.customer_id = t2.customer_id group by t1.customer_id
Also show their customer ids.
select t1.customer_id, t2.customer_first_name, t2.customer_last_name, count(*) from accounts as t1 join customers as t2 on t1.customer_id = t2.customer_id group by t1.customer_id