php mysql一对多查询

-- users 表结构
CREATE TABLE users (
    id INT PRIMARY KEY AUTO_INCREMENT,
    name VARCHAR(100)
);

-- orders 表结构
CREATE TABLE orders (
    id INT PRIMARY KEY AUTO_INCREMENT,
    user_id INT,
    amount DECIMAL(10, 2),
    FOREIGN KEY (user_id) REFERENCES users(id)
);

<?php
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "database_name";

// 创建连接
$conn = new mysqli($servername, $username, $password, $dbname);

// 检查连接
if ($conn->connect_error) {
    die("连接失败: " . $conn->connect_error);
}

// 查询某个用户的所有订单
$user_id = 1;
$sql = "SELECT orders.id, orders.amount FROM orders JOIN users ON orders.user_id = users.id WHERE users.id = ?";
$stmt = $conn->prepare($sql);
$stmt->bind_param("i", $user_id);
$stmt->execute();
$result = $stmt->get_result();

while ($row = $result->fetch_assoc()) {
    echo "Order ID: " . $row["id"] . " - Amount: " . $row["amount"] . "<br>";
}

$stmt->close();
$conn->close();
?>