text: CREATE TABLE `t_stock` (
    `id` int(11) NOT NULL AUTO_INCREMENT,
    `stock` int(11) NOT NULL DEFAULT '100',
    PRIMARY KEY (`id`)
  );
  
  create TABLE t_cart (
    id int PRIMARY KEY AUTO_INCREMENT,
    stockId int not null,
    userId int not null,
    cart_num int not null DEFAULT 1
  );