QuerydrillCustomers from the same country
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
Return each pair of customer names that share a country, listing every pair once with the lower customer id first.
What this exercise teaches
The a.id < b.id condition is the standard trick to list each pair once.
A hint if you get stuck
Self join on country, and use a.id < b.id to avoid duplicates and self-pairs.
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