Show me the first name of all customers.
select first_name from customers
How many bookings are there in record?
select count(*) from bookings
What about that in terms of those customers?
select t1.first_name, count(*) from customers as t1 join bookings as t2 on t1.customer_id = t2.customer_id group by t1.customer_id
Could you also show me those customers' ids?
select t1.customer_id, t1.first_name, count(*) from customers as t1 join bookings as t2 on t1.customer_id = t2.customer_id group by t1.customer_id