【发布时间】：2023-03-08 07:00:02
【问题描述】：
我想创建名为 Customer 和 Orders 的 SQL 数据库表 SQL：
CREATE TABLE Customer (
customer_id INT NOT NULL AUTO_INCREMENT,
customer_name VARCHAR(255) UNIQUE,
PRIMARY KEY (customer_id)
);
CREATE TABLE Orders (
order_id INT NOT NULL AUTO_INCREMENT,
customer_name VARCHAR(255),
order_date DATETIME,
PRIMARY KEY(order_id),
FOREIGN KEY (customer_name) REFERENCES Customer(customer_name)
ON UPDATE CASCADE
ON DELETE CASCADE
);
之后，我想插入一个带有对 Customer 对象的引用的 Orders 对象。 Java 和休眠：
Transaction tx = session.beginTransaction();
Customer cu = (Customer) session.load(Customer.class, 1);
Date d = new Date();
Orders od = new Orders(cu, d);
od.setCustomer(cu);
Set<Orders> hs = new HashSet<Orders>();
hs.add(od);
cu.setOrderses(hs);
session.save(cu);
session.save(od);
tx.commit();
插入返回异常： 无法添加或更新子行：外键约束失败 我所做的一切都与 Hibernate 教程中的完全一样。 我做错了什么？
Java 类
public class Customer implements java.io.Serializable {
private Integer customerId;
private String customerName;
private Set<Orders> orderses = new HashSet<Orders>(0);
public Customer() {
}
public Customer(String customerName, Set<Orders> orderses) {
this.customerName = customerName;
this.orderses = orderses;
}
public Integer getCustomerId() {
return this.customerId;
}
public void setCustomerId(Integer customerId) {
this.customerId = customerId;
}
public String getCustomerName() {
return this.customerName;
}
public void setCustomerName(String customerName) {
this.customerName = customerName;
}
public Set<Orders> getOrderses() {
return this.orderses;
}
public void setOrderses(Set<Orders> orderses) {
this.orderses = orderses;
}
}
public class Orders implements java.io.Serializable {
private Integer orderId;
private Customer customer;
private Date orderDate;
public Orders() {
}
public Orders(Customer customer, Date orderDate) {
this.customer = customer;
this.orderDate = orderDate;
}
public Integer getOrderId() {
return this.orderId;
}
public void setOrderId(Integer orderId) {
this.orderId = orderId;
}
public Customer getCustomer() {
return this.customer;
}
public void setCustomer(Customer customer) {
this.customer = customer;
}
public Date getOrderDate() {
return this.orderDate;
}
public void setOrderDate(Date orderDate) {
this.orderDate = orderDate;
}
}
【问题讨论】：
-
我认为您认为您不需要明确保存订单，当您保存客户时，hibernate会为您完成。
-
我尝试了两种方式：使用级联和不使用级联：两者都返回相同的异常
-
你能分享一下 Customer 和 Orders 类的代码吗？
-
您使用 customer_name 作为外键而不是 customer_id 有什么原因吗？
-
customer_name 是包含相关名称的替代唯一键