问题描述
现在有三张数据表，表名为orders,orderdetail,items，分别表示订单，订单详情，商品。
![表关系](https://www.cppentry.com/upload_files/article/57/1_tiwzb__.png "\")
其中一个订单包含多个订单详情，表示订单中的不同个具体的商品，订单详情唯一对应一件商品。所以orderdetail中的外键order_id为orders的主键，orderdetail中的外键items_id为items的主键。
数据库结构
DROP TABLE IF EXISTS `items`;
/*!40101 SET @saved_cs_client = @@character_set_client */;
/*!40101 SET character_set_client = utf8 */;
CREATE TABLE `items` (
`id` int(11) NOT NULL auto_increment,
`name` varchar(32) NOT NULL COMMENT '商品名称',
`price` float(10,1) NOT NULL COMMENT '商品定价',
`detail` text COMMENT '商品描述',
`pic` varchar(64) default NULL COMMENT '商品图片',
`createtime` datetime NOT NULL COMMENT '生产日期',
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=6 DEFAULT CHARSET=utf8;
/*!40101 SET character_set_client = @saved_cs_client */;
--
-- Table structure for table `orderdetail`
--
DROP TABLE IF EXISTS `orderdetail`;
/*!40101 SET @saved_cs_client = @@character_set_client */;
/*!40101 SET character_set_client = utf8 */;
CREATE TABLE `orderdetail` (
`id` int(11) NOT NULL auto_increment,
`orders_id` int(11) NOT NULL COMMENT '订单id',
`items_id` int(11) NOT NULL COMMENT '商品id',
`items_num` int(11) default NULL COMMENT '商品购买数量',
PRIMARY KEY (`id`),
KEY `FK_orderdetail_1` (`orders_id`),
KEY `FK_orderdetail_2` (`items_id`),
CONSTRAINT `FK_orderdetail_1` FOREIGN KEY (`orders_id`) REFERENCES `orders` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION,
CONSTRAINT `FK_orderdetail_2` FOREIGN KEY (`items_id`) REFERENCES `items` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION
) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8;
/*!40101 SET character_set_client = @saved_cs_client */;
--
-- Table structure for table `orders`
--
DROP TABLE IF EXISTS `orders`;
/*!40101 SET @saved_cs_client = @@character_set_client */;
/*!40101 SET character_set_client = utf8 */;
CREATE TABLE `orders` (
`id` int(11) NOT NULL auto_increment,
`user_id` int(11) NOT NULL COMMENT '下单用户id',
`number` varchar(32) NOT NULL COMMENT '订单号',
`createtime` datetime NOT NULL COMMENT '创建订单时间',
`note` varchar(100) default NULL COMMENT '备注',
PRIMARY KEY (`id`),
KEY `FK_orders_1` (`user_id`),
CONSTRAINT `FK_orders_id` FOREIGN KEY (`user_id`) REFERENCES `user` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION
) ENGINE=InnoDB AUTO_INCREMENT=6 DEFAULT CHARSET=utf8;
POJO
根据表创建pojo类：
Items.java
package cn.elinzhou.mybatisTest.pojo; import java.util.Date; /** * Description: Items * Author: Elin Zhou * Create: 2015-06-30 00:57 */ public class Items { private Integer id; private String name; private Double price; private String detail; private String pic; private Date createtime; public Date getCreatetime() { return createtime; } public void setCreatetime(Date createtime) { this.createtime = createtime; } public String getDetail() { return detail; } public void setDetail(String detail) { this.detail = detail; } public Integer getId() { return id; } public void setId(Integer id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getPic() { return pic; } public void setPic(String pic) { this.pic = pic; } public Double getPrice() { return price; } public void setPrice(Double price) { this.price = price; } @Override public String toString() { return "Items{" + "createtime=" + createtime + ", id=" + id + ", name='" + name + '\'' + ", price=" + price + ", detail='" + detail + '\'' + ", pic=