Using sales table (id, product, category, amount, region, sale_date), write queries: (1) Total sales per category, (2) Average sale amount per region, (3) Count of sales per product, sorted by count DESC, (4) Categories with total sales > $10,000 (HAVING), (5) Monthly sales trend (GROUP BY YEAR, MONTH), (6) Running total using window function SUM() OVER().
