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Optimize a query fetching customer data with a rolling 6-month sales sum.

SQLmedium0.4 min readPremium
Frequency
Low
Asked at 1 company
Category
487
questions in SQL
Difficulty Split
130E|271M|86H
in this category
Total Bank
1,863
across 7 categories
Asked at these companies
Fragma Data Systems
Key Concepts Tested
partitionwindow
Expert AnswerPremium
82 wordsInterview-ready
Rolling 6-month sum: use window functions. SELECT customer_id, SUM(amount) OVER (PARTITION BY customer_id ORDER BY sale_date ROWS BETWEEN 5 PRECEDING AND CURRENT ROW) AS rolling_6m FROM sales. Or RANGE for actual 6 months. Optimize: partition table by customer_id or date; index on (customer_id, sale_date). Pre-aggregate in summary table if queried often. **Why it matters**: Design choices compound at scale—wrong approach can cause 100× overhead....
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