For each product that has been ordered, return its revenue (SUM(qty * unit_price)) AND its share of the category total.
Skip products with no order_items rows.
Columns: product_id, category, product_revenue, ROUND(pct_of_category, 2) AS pct_of_category (as percent, e.g. 66.67 for 66.67%). Sort by product_id ascending.