intermediateJava 8 & Streams163 of 436
How would you find duplicate records in a table without using GROUP BY?
Tests whether you reach for a self-join on the matching columns with a row-identity inequality (or a window function like ROW_NUMBER() OVER (PARTITION BY ...)) to flag duplicates, showing you know more than one way to express 'duplicate' in SQL beyond the obvious GROUP BY + HAVING COUNT(*) > 1.
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