What is the most frequently used payment method?
select payment_method from customers group by payment_method order by count ( * ) desc limit 1
How many customers used Visa to pay?
select count ( * ) from customers group by payment_method having payment_method = "Visa"
Can you show me the email addresses of all the customers who paid with Visa?
select customer_email from customers where payment_method = "Visa"
How about their phone numbers?
select customer_phone from customers where payment_method = "Visa"
Who is the newest customer of that group?
select customer_name from customers where payment_method = "Visa" order by date_became_customer limit 1
When did that customer become a customer?
select date_became_customer from customers where payment_method = "Visa" order by date_became_customer limit 1