数据库设计

-- 类目
create table `product_category` (
    `category_id` int not null auto_increment,
    `category_name` varchar(64) not null comment '类目名字',
    `category_type` int not null comment '类目编号',
    `create_time` timestamp not null default current_timestamp comment '创建时间',
    `update_time` timestamp not null default current_timestamp on update current_timestamp comment '修改时间',
    primary key (`category_id`),
    unique key `uqe_category_type` (`category_type`)
);

-- 商品
create table `product_info` (
    `product_id` varchar(32) not null,
    `product_name` varchar(64) not null comment '商品名称',
    `product_price` decimal(8,2) not null comment '单价',
    `product_stock` int not null comment '库存',
    `product_description` varchar(64) comment '描述',
    `product_icon` varchar(512) comment '小图',
    `product_status` tinyint(3) DEFAULT '0' COMMENT '商品状态,0正常1下架',
    `category_type` int not null comment '类目编号',
    `create_time` timestamp not null default current_timestamp comment '创建时间',
    `update_time` timestamp not null default current_timestamp on update current_timestamp comment '修改时间',
    primary key (`product_id`)
);

-- 订单
create table `order_master` (
    `order_id` varchar(32) not null,
    `buyer_name` varchar(32) not null comment '买家名字',
    `buyer_phone` varchar(32) not null comment '买家电话',
    `buyer_address` varchar(128) not null comment '买家地址',
    `buyer_openid` varchar(64) not null comment '买家微信openid',
    `order_amount` decimal(8,2) not null comment '订单总金额',
    `order_status` tinyint(3) not null default '0' comment '订单状态, 默认为新下单',
    `pay_status` tinyint(3) not null default '0' comment '支付状态, 默认未支付',
    `create_time` timestamp not null default current_timestamp comment '创建时间',
    `update_time` timestamp not null default current_timestamp on update current_timestamp comment '修改时间',
    primary key (`order_id`),
    key `idx_buyer_openid` (`buyer_openid`)
);

-- 订单商品
create table `order_detail` (
    `detail_id` varchar(32) not null,
    `order_id` varchar(32) not null,
    `product_id` varchar(32) not null,
    `product_name` varchar(64) not null comment '商品名称',
    `product_price` decimal(8,2) not null comment '当前价格,单位分',
    `product_quantity` int not null comment '数量',
    `product_icon` varchar(512) comment '小图',
    `create_time` timestamp not null default current_timestamp comment '创建时间',
    `update_time` timestamp not null default current_timestamp on update current_timestamp comment '修改时间',
    primary key (`detail_id`),
    key `idx_order_id` (`order_id`),
    foreign key(`order_id`) REFERENCES order_master(`order_id`)
);

-- 卖家(登录后台使用, 卖家登录之后可能直接采用微信扫码登录，不使用账号密码)
create table `seller_info` (
    `id` varchar(32) not null,
    `username` varchar(32) not null,
    `password` varchar(32) not null,
    `openid` varchar(64) not null comment '微信openid',
    `create_time` timestamp not null default current_timestamp comment '创建时间',
    `update_time` timestamp not null default current_timestamp on update current_timestamp comment '修改时间',
    primary key (`id`)
) comment '卖家信息表';

 关于timestamp和datetime：

http://www.cnblogs.com/ivictor/p/5028368.html

https://dev.mysql.com/doc/refman/5.7/en/datetime.html