如何在MYSQL中存储PDF文件的文件引用以在php中检索

<?php
// 连接到MYSQL数据库
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "database";

$conn = new mysqli($servername, $username, $password, $dbname);
if ($conn->connect_error) {
    die("连接失败: " . $conn->connect_error);
}

// 创建文件引用表
$sql = "CREATE TABLE IF NOT EXISTS pdf_files (
    id INT(6) UNSIGNED AUTO_INCREMENT PRIMARY KEY,
    filename VARCHAR(255) NOT NULL,
    filepath VARCHAR(255) NOT NULL
)";
if ($conn->query($sql) === FALSE) {
    echo "创建表失败: " . $conn->error;
}

// 处理文件上传
if ($_FILES["pdf_file"]["error"] == UPLOAD_ERR_OK) {
    $filename = $_FILES["pdf_file"]["name"];
    $filepath = "uploads/" . $filename;

    // 将文件名和文件路径保存到数据库
    $sql = "INSERT INTO pdf_files (filename, filepath) VALUES ('$filename', '$filepath')";
    if ($conn->query($sql) === FALSE) {
        echo "保存文件引用失败: " . $conn->error;
    }

    // 将文件移动到服务器上的指定目录
    move_uploaded_file($_FILES["pdf_file"]["tmp_name"], $filepath);
}

// 检索文件引用
$sql = "SELECT filename, filepath FROM pdf_files";
$result = $conn->query($sql);

if ($result->num_rows > 0) {
    // 输出每个文件的链接
    while ($row = $result->fetch_assoc()) {
        $filename = $row["filename"];
        $filepath = $row["filepath"];
        echo "<a href='$filepath'>$filename</a><br>";
    }
} else {
    echo "没有找到任何文件";
}

$conn->close();
?>