新手轻喷。小弟在看head first 的 PHP & MySQL，第二章用命令行创建数据库：

tony@Tony-Laptop-Ubuntu$ ~ mysql
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 41
Server version: 5.5.29-0ubuntu0.12.04.1 (Ubuntu)

Copyright (c) 2000, 2012, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> CREATE DATABASE aliendatabase;
ERROR 1044 (42000): Access denied for user ''@'localhost' to database 'aliendatabase'

求大神解释加解决方案～小弟拜谢！