如何将成员表与登录成员下的玩家表结合起来

我正在制作一个网站，您需要注册，然后创建一个角色玩。我如何将注册页面中使用的表格与玩家的表格结合起来，以便玩家总是获得他创建的角色。

我有一个名为user的表成员来存储注册用户和一个表玩家的字符

我查看了session_id，但据我所知，我不能将数据存储到mysql表中。

我还考虑在创建时将成员表中的用户名和电子邮件添加到球员表中，但我失败了。我想我可以说，如果用户名和ID在两个表中都是相同的，那么玩家。

我对这一切都是新手。

这是寄存器代码

<?php
include_once 'db_connect.php';
include_once 'psl-config.php';
$error_msg = "";
$now = time();

if (isset($_POST['username'], $_POST['email'], $_POST['p'])) {
    // Sanitize and validate the data passed in
    $username = filter_input(INPUT_POST, 'username', FILTER_SANITIZE_STRING);
    $email = filter_input(INPUT_POST, 'email', FILTER_SANITIZE_EMAIL);
    $email = filter_var($email, FILTER_VALIDATE_EMAIL);
    if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
        // Not a valid email
        $error_msg .= '<p class="error">The email address you entered is not valid</p>';
    }
    $password = filter_input(INPUT_POST, 'p', FILTER_SANITIZE_STRING);
    if (strlen($password) != 128) {
        // The hashed pwd should be 128 characters long.
        // If it's not, something really odd has happened
        $error_msg .= '<p class="error">Invalid password configuration.</p>';
    }
    // Username validity and password validity have been checked client side.
    // This should should be adequate as nobody gains any advantage from
    // breaking these rules.
    //
    $prep_stmt = "SELECT id FROM members WHERE email = ? LIMIT 1";
    $stmt = $mysqli->prepare($prep_stmt);
   // check existing email  
    if ($stmt) {
        $stmt->bind_param('s', $email);
        $stmt->execute();
        $stmt->store_result();
        if ($stmt->num_rows == 1) {
            // A user with this email address already exists
            $error_msg .= '<p class="error">A user with this email address already exists.</p>';
                        $stmt->close();
        }
                $stmt->close();
    } else {
        $error_msg .= '<p class="error">Database error Line 39</p>';
                $stmt->close();
    }
    // check existing username
    $prep_stmt = "SELECT id FROM members WHERE username = ? LIMIT 1";
    $stmt = $mysqli->prepare($prep_stmt);
    if ($stmt) {
        $stmt->bind_param('s', $username);
        $stmt->execute();
        $stmt->store_result();
                if ($stmt->num_rows == 1) {
                        // A user with this username already exists
                        $error_msg .= '<p class="error">A user with this username already exists</p>';
                        $stmt->close();
                }
                $stmt->close();
        } else {
                $error_msg .= '<p class="error">Database error line 55</p>';
                $stmt->close();
        }
    // TODO: 
    // We'll also have to account for the situation where the user doesn't have
    // rights to do registration, by checking what type of user is attempting to
    // perform the operation.
    if (empty($error_msg)) {
        // Create a random salt
        //$random_salt = hash('sha512', uniqid(openssl_random_pseudo_bytes(16), TRUE)); // Did not work
        $random_salt = hash('sha512', uniqid(mt_rand(1, mt_getrandmax()), true));
        // Create salted password 
        $password = hash('sha512', $password . $random_salt);

        // Insert the new user into the database
        // Add here wat you want to add into the database at account creation  
        if ($insert_stmt = $mysqli->prepare("INSERT INTO members (username, email, password, salt, accdate) VALUES (?, ?, ?, ?, now())")) {
            $insert_stmt->bind_param('ssss', $username, $email, $password, $random_salt);
            // Execute the prepared query.
            if (! $insert_stmt->execute()) {
                header('Location: ../error.php?err=Registration failure: INSERT');
            }
        }
        header('Location: ./register_success.php');
    }
}

谁能给我指个正确的方向?由于

table user, 
id, name, login, password  etc...
table character
id, user_id, character_name, hp, etc..

SELECT u.*, c.* FROM users AS u JOIN characters AS c ON u.id = c.user_id WHERE u.id = $user_id.