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Churned customers
Customer retention charts
10. Question 1


Let's start with Question 1!


Find the number of churned customers in weekly registration cohorts. Show the following columns: year, week, and churned_customers. Define churned customers as customers who haven't placed an order in the last 90 days. Order the results by year and week.

Don't show the rows for which the number of churned customers is 0.

Stuck? Here's a hint!