SELECT P.reference as SKU, PL.`name` as Product_Name, COUNT(OD.id_order) as ordered_qty FROM ps_product P
LEFT JOIN ps_product_lang PL ON P.id_product = PL.id_product
LEFT JOIN ps_order_detail OD ON P.id_product = OD.product_id
LEFT JOIN ps_orders O ON O.id_order = OD.id_order
WHERE O.valid = 1
GROUP BY P.reference, PL.`name`
ORDER BY ordered_qty DESC