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What is the QUALIFY clause, and how does it simplify filtering on window functions?

You cannot filter on a window function in WHERE, so people wrap queries in subqueries. QUALIFY filters window results directly. The signal is knowing why WHERE cannot do it and writing top-N-per-group cleanly.

Updated Aug 2026 · Grounded in real Applied AI Engineer interview loops and written to a senior-engineer editorial bar.

You cannot filter on a window function in WHERE, so people wrap queries in subqueries. QUALIFY filters window results directly. The signal is knowing why WHERE cannot do it and writing top-N-per-group cleanly.

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