goods表

mysql> create table if not exists goods(
    -> goods_id int primary key auto_increment comment '商品编号',
    -> goods_name varchar(32) not null comment '商品名称',
    -> unitprice int not null default 0 comment '单价，单位分',
    -> category varchar(12) comment '商品分类',
    -> provider varchar(64) not null comment '供应商名称');

customer表 

mysql> create table customer(
    -> customer_id int primary key auto_increment comment '客户号',
    -> name varchar(32) not null comment '姓名',
    -> address varchar(64) comment '住址',
    -> email varchar(32) unique key comment '邮箱',
    -> sex enum('男','女') not null comment '性别',
    -> card_id char(18) unique key comment '身份证');

purchase表 

mysql> create table purchase(
    -> order_id int primary key auto_increment comment '购买订单号',
    -> customer_id int comment '客户号',
    -> goods_id int comment '商品号',
    -> nums int not null comment '购买数量',
    -> foreign key (customer_id) references customer(customer_id),
    -> foreign key (goods_id) references goods(goods_id));