What is a window function and how is it different from GROUP BY?

SQL window functions · Freshers and experienced

Model answer

A window function calculates over a set of related rows without collapsing them: SUM(amount) OVER (PARTITION BY customer_id). GROUP BY returns one row per group, while a window function keeps every row and adds the calculated value.

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Window Functions: ROW_NUMBER, RANK and Running Totals in the course SQL for Beginners: Learn Databases Step by Step.

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