What payment method did Dr. Julia Wuckert MD use?
select payment_method from customers where customer_name = "Dr. julia wuckert MD"
How many customers used credit cards?
?
select count ( customer_id ) from customers where payment_method = "Credit Card"
From when did Rodrick Heaney became a customer?
select t1.active_from_date from customer_contact_channels as t1 join customers as t2 on t1.customer_id = t2.customer_id where t2.customer_name = "Rodrick Heaney"