我有两个表:product(idproduct,name,description,tax)product_storage(idstorage,idproduct,added,quantity,price)对于每个产品，它可能有不同的价格，最旧的是“先到先得”例如在存储中我有:1,1,2010-01-01,0,10.02,1,2010-01-02,0,11.03,1,2010-01-03,10,12.04,2,2010-01-04,0,12.05,2,2010-01-05,10,11.06,2,2010-01-06,10,13.07,3,2010-01-07,10,14.08,3,201