MySQL解决外键约束冲突的详细步骤和代码示例

CREATE TABLE customers (
    id INT PRIMARY KEY,
    name VARCHAR(255)
);

CREATE TABLE orders (
    id INT PRIMARY KEY,
    customer_id INT,
    order_date DATE,
    FOREIGN KEY (customer_id) REFERENCES customers(id)
);

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;

public class InsertOrder {
    private static final String DB_URL = "jdbc:mysql://your_host/your_database";
    private static final String DB_USER = "your_user";
    private static final String DB_PASSWORD = "your_password";

    public static void main(String[] args) {
        try (Connection conn = DriverManager.getConnection(DB_URL, DB_USER, DB_PASSWORD)) {
            // 首先插入客户数据
            String insertCustomerQuery = "INSERT INTO customers (id, name) VALUES (?, ?)";
            try (PreparedStatement customerStmt = conn.prepareStatement(insertCustomerQuery)) {
                customerStmt.setInt(1, 1);
                customerStmt.setString(2, "John Doe");
                customerStmt.executeUpdate();
            }

            // 然后插入订单数据
            String insertOrderQuery = "INSERT INTO orders (id, customer_id, order_date) VALUES (?, ?, ?)";
            try (PreparedStatement orderStmt = conn.prepareStatement(insertOrderQuery)) {
                orderStmt.setInt(1, 101);
                orderStmt.setInt(2, 1); // customer_id 必须存在于 customers 表中
                orderStmt.setDate(3, java.sql.Date.valueOf("2023-01-01"));
                orderStmt.executeUpdate();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

public class DeleteCustomer {
    private static final String DB_URL = "jdbc:mysql://your_host/your_database";
    private static final String DB_USER = "your_user";
    private static final String DB_PASSWORD = "your_password";

    public static void main(String[] args) {
        try (Connection conn = DriverManager.getConnection(DB_URL, DB_USER, DB_PASSWORD)) {
            // 首先删除依赖的订单数据
            String deleteOrdersQuery = "DELETE FROM orders WHERE customer_id = ?";
            try (PreparedStatement orderStmt = conn.prepareStatement(deleteOrdersQuery)) {
                orderStmt.setInt(1, 1);
                orderStmt.executeUpdate();
            }

            // 然后删除客户数据
            String deleteCustomerQuery = "DELETE FROM customers WHERE id = ?";
            try (PreparedStatement customerStmt = conn.prepareStatement(deleteCustomerQuery)) {
                customerStmt.setInt(1, 1);
                customerStmt.executeUpdate();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

CREATE TABLE customers (
    id INT PRIMARY KEY,
    name VARCHAR(255)
);

CREATE TABLE orders (
    id INT PRIMARY KEY,
    customer_id INT,
    order_date DATE,
    FOREIGN KEY (customer_id) REFERENCES customers(id) ON DELETE CASCADE ON UPDATE CASCADE
);

-- 验证外键约束
SELECT 
    TABLE_NAME, 
    COLUMN_NAME, 
    CONSTRAINT_NAME, 
    REFERENCED_TABLE_NAME, 
    REFERENCED_COLUMN_NAME
FROM
    INFORMATION_SCHEMA.KEY_COLUMN_USAGE
WHERE
    REFERENCED_TABLE_NAME = 'customers';