ALTER TABLE vn.item ADD weightByPiece int unsigned NULL
COMMENT 'peso por defecto para un articulo por tallo/unidad';
/*
-- actualizamos con los valores del itemCost, o de la ultima compra, o de la densidad * volumen
UPDATE vn.itemCost ic 
		JOIN cache.last_buy lb ON lb.item_id = ic.itemFk and lb.warehouse_id = ic.warehouseFk
		JOIN vn.buy b ON b.id = lb.buy_id 
		JOIN vn.item i ON i.id = ic.itemFk 
	SET ic.grams  = COALESCE(
		(b.weight * 1000) / b.packing, 
		i.density * (cm3delivery / 1000000) * 1000);

UPDATE vn.item i
		JOIN vn.itemCost ic ON ic.itemFk = i.id and ic.warehouseFk = 60 
	SET i.weightByPiece = ic.grams
	WHERE i.weightByPiece IS NULL;

UPDATE vn.item i
		JOIN vn.itemCost ic ON ic.itemFk = i.id and ic.warehouseFk = 7
	SET i.weightByPiece = ic.grams
	WHERE weightByPiece IS NULL;

UPDATE vn.item i
		JOIN vn.itemCost ic ON ic.itemFk = i.id
	SET i.weightByPiece = ic.grams
	WHERE i.weightByPiece IS NULL
		AND ic.warehouseFk NOT IN (60,7);*/