SELECT t1.*, t4.* FROM detalle_venta AS t1
INNER JOIN detalle_compra AS t2 ON t1.producto_idproducto = t2.producto_idproducto
INNER JOIN compra AS t3 ON t2.compra_idcompra = t3.idcompra
INNER JOIN proveedor AS t4 ON t3.proveedor_idproveedor = t4.idproveedor