JAVA全系列 教程
3762个小节阅读:7089.9k
目录
C语言快速入门
JAVA全系列 教程
面向对象的程序设计语言
Python全系列 教程
Python3.x版本,未来主流的版本
人工智能 教程
顺势而为,AI创新未来
大厂算法 教程
算法,程序员自我提升必经之路
C++ 教程
一门通用计算机编程语言
微服务 教程
目前业界流行的框架组合
web前端全系列 教程
通向WEB技术世界的钥匙
大数据全系列 教程
站在云端操控万千数据
AIGC全能工具班
A A
White Night
创建表
orders表
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CREATE TABLE `orders` (
`orderid` int(11) NOT NULL AUTO_INCREMENT,
`orderprice` float(11,2) DEFAULT NULL,
`user_id` int(11) DEFAULT NULL,
PRIMARY KEY (`orderid`),
KEY `orders_fk` (`user_id`),
CONSTRAINT `orders_fk` FOREIGN KEY (`user_id`) REFERENCES `users` (`userid`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
items表
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CREATE TABLE `items` (
`itemid` int(11) NOT NULL,
`itemname` varchar(30) DEFAULT NULL,
`itemprice` float(11,2) DEFAULT NULL,
`itemnum` int(11) DEFAULT NULL,
PRIMARY KEY (`itemid`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
orders_itmes表
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CREATE TABLE `orders_items` (
`order_id` int(11) NOT NULL,
`item_id` int(11) NOT NULL,
PRIMARY KEY (`order_id`,`item_id`),
KEY `orders_items_fk2` (`item_id`),
CONSTRAINT `orders_items_fk` FOREIGN KEY (`order_id`) REFERENCES `orders` (`orderid`),
CONSTRAINT `orders_items_fk2` FOREIGN KEY (`item_id`) REFERENCES `items` (`itemid`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
对象的关联关系
Users对象
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public class Users {
private int userid;
private String username;
private int userage;
//创建与Orders的关联关系
private List<Orders> orders = new ArrayList<>();
public List<Orders> getOrders() {
return orders;
}
public void setOrders(List<Orders> orders) {
this.orders = orders;
}
@Override
public String toString() {
return "Users{" +
"userid=" + userid +
", username='" + username + '\'' +
", userage=" + userage +
'}';
}
public int getUserid() {
return userid;
}
public void setUserid(int userid) {
this.userid = userid;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public int getUserage() {
return userage;
}
public void setUserage(int userage) {
this.userage = userage;
}
}
Orders对象
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public class Orders {
private int orderid;
private double orderprice;
//关联Users
private Users users;
//关联Items
private List<Items> items =new ArrayList<>();
public int getOrderid() {
return orderid;
}
public void setOrderid(int orderid) {
this.orderid = orderid;
}
public double getOrderprice() {
return orderprice;
}
public void setOrderprice(double orderprice) {
this.orderprice = orderprice;
}
public Users getUsers() {
return users;
}
public void setUsers(Users users) {
this.users = users;
}
public List<Items> getItems() {
return items;
}
public void setItems(List<Items> items) {
this.items = items;
}
}
Items对象
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public class Items {
private int itemid;
private String itemname;
private double itemprice;
private int itemnum;
//关联Orders
private List<Orders> orders = new ArrayList<>();
public int getItemid() {
return itemid;
}
public void setItemid(int itemid) {
this.itemid = itemid;
}
public String getItemname() {
return itemname;
}
public void setItemname(String itemname) {
this.itemname = itemname;
}
public double getItemprice() {
return itemprice;
}
public void setItemprice(double itemprice) {
this.itemprice = itemprice;
}
public int getItemnum() {
return itemnum;
}
public void setItemnum(int itemnum) {
this.itemnum = itemnum;
}
public List<Orders> getOrders() {
return orders;
}
public void setOrders(List<Orders> orders) {
this.orders = orders;
}
}