QuerydrillEach customer's first order
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 each customer, return the customer_id and the id of their first order (earliest date, then lowest id). Count every order, whatever the status.
What this exercise teaches
ROW_NUMBER picks exactly one row per group, even when values tie.
A hint if you get stuck
ROW_NUMBER() per customer in a subquery, keep row 1.
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