Number of orders by product in Spree 2.0+

spree2_orders_by_product.sql

SELECT p.id,
sum(quantity) AS num_sold
FROM spree_orders o
JOIN spree_line_items li ON o.ID = li.order_id
JOIN spree_variants v ON li.variant_id = v.id
JOIN spree_stock_items i ON v.id = i.variant_id
JOIN spree_products p ON v.product_id = p.id
WHERE o.state = 'complete'
GROUP BY p.id