QuerydrillActive in several months
An SQL exercise from Querydrill. Solve it with a SQL editor in your browser, checked on the rows it returns and again on changed data, and it is checked the moment you submit.
The task
For customers who ordered in at least two different months, return the customer_id and the number of different months they ordered in. Count every order, whatever the status.
What this exercise teaches
COUNT(DISTINCT ...) in HAVING is how you measure activity across periods.
A hint if you get stuck
COUNT(DISTINCT month expression) per customer, then HAVING on it.
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