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-- Revenue by region with rolling 30-day avg
SELECT
  o.region,
  SUM(o.total_amount) AS revenue,
  AVG(SUM(o.total_amount)) OVER (
    PARTITION BY o.region
    ORDER BY o.order_date
    ROWS BETWEEN 29 PRECEDING AND CURRENT ROW
  ) AS rolling_avg
FROM orders o
JOIN  products p USING (product_id)
WHERE o.status = 'completed'
GROUP BY o.region, o.order_date
ORDER BY revenue DESC
LIMIT 10;