Row count for DISTINCT over a GROUP BY aggregate

#709

Avito asks a classic interview gotcha: does the candidate know that DISTINCT on top of GROUP BY is almost always a no-op? Here is a tiny repro of the same trick on click-analytics data. Run the query against the seed data and return how many rows it produces: Return the result in a single column rows_returned — the count of rows the query above yields on the seed data (i.e. wrap the query and COUNT(*) over it).

Expected output sample

This is what a correct answer looks like — its row count is its own, it doesn't have to match the schema tables.

rows_returned
11

Avito

Your query result will appear here

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