Growth teams track time to activation: how long new customers take to place their first order.
For every customer who has ordered, return name and days_to_first_order: the whole number of days between their signup_date and their earliest order_date.
Sort by days_to_first_order, then name. Customers who never ordered are left out.
Schema
customers(id, name, country, signup_date)
orders(id, customer_id, order_date, total)