Cumulative Sales Percentage — Solution & ExplanationProblems / Cumulative Sales Percentage / EditorialApproachThis problem combines two window function patterns:1. Partition Total (Unbounded Window)SUM(sales_amount) OVER (PARTITION BY category) — no ORDER BY means the frame spans the entire partition, giving the category total on every row.2. Cumulative Sum (Ordered Window)SUM(sales_amount) OVER (PARTITION BY category ORDER BY sales_amount DESC) — with ORDER BY, the default frame is RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW, producing a running total.3. PercentageDivide the cumulative sum by the partition total. Use 100.0 * to force float division, and ROUND(..., 2) for clean output.Use CaseCumulative percentage analysis (Pareto analysis) helps identify which products contribute most to category revenue — the classic 80/20 rule.Hints

SUM(...) OVER (PARTITION BY category) without ORDER BY gives the total for the entire partition.

SUM(...) OVER (PARTITION BY category ORDER BY sales_amount DESC) gives a running total from highest to lowest.

Divide the cumulative sum by the partition total and multiply by 100 for the percentage.

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