Compute revenue per product category from order_items (revenue = qty * unit_price, joined to products for the category), then build a Pareto / 80-20 view.
Columns: - category - revenue — total for the category - pct_of_total — this category's share of all revenue, 1 decimal - cumulative_pct — running share as you walk categories from largest to smallest revenue, 1 decimal (the last row reaches 100.0)
Sort by revenue descending (ties by category).