无法从表中选择，但我可以插入和创建

mysql有这个非常奇怪的问题。我可以插入并创建表。但是我无法选择任何内容，并且在我尝试时它不会显示任何错误，它只是呼应我的行"错误："

getDiff("validTable");
function getDiff($regNr) {
    global $servername, $username, $password, $dbname;
    // Create connection
    $conn = new mysqli($servername, $username, $password, $dbname);
    // Check connection
    if ($conn->connect_error) {
        die("Connection failed: " . $conn->connect_error);
    }
    //todo
    $sql = "SELECT * FROM $regNr ORDER BY id LIMIT 1";
    $result = $conn->query($sql);
    if ($result === TRUE) {
        echo "done";
    } else {
        $error = $result->error;
        echo "Error: " . $error;
    }
    $conn->close();
}

但是当我使用它插入数据库时

$query = "CREATE TABLE IF NOT EXISTS $regNr ( `id` MEDIUMINT NOT NULL AUTO_INCREMENT, `mail` INT NOT NULL , `price` INT NOT NULL , `views` INT NOT NULL , `the_date` DATE NOT NULL , `time` VARCHAR(5) NOT NULL, PRIMARY KEY (id) )";
runQuery($query);
function runQuery($todo) {
   global $servername, $username, $password, $dbname;
   // Create connection
   $conn = new mysqli($servername, $username, $password, $dbname);
   // Check connection
   if ($conn->connect_error) {
       die("Connection failed: " . $conn->connect_error);
   }
   //todo
   $sql = $todo;
   if ($conn->query($sql) === TRUE) {
       echo "done";
   } else {
       echo "Error: " . $conn->error;
   }
   $conn->close();
}

它工作得很好，很花花公子。我做错了什么？！这简直让我发疯了！