1、默认情况下，mysql不需要输入用户名和密码，就可以登录
C:\Users\linzm>mysql
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 1
Server version: 5.5.32-log MySQL Community Server (GPL)
Copyright (c) 2000, 2013, 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.
2、因为默认安装的mysql，有空用户名的记录
mysql> select count(*) from user where user='';
+----------+
| count(*) |
+----------+
| 1 |
+----------+
1 row in set (0.00 sec)
3、为了安全考虑，需要删除这个功能，可以登录进去mysql，删除掉
mysql>use mysql;
mysql>delete from user where user='';
mysql>flush privileges; (必须的)
4、检查修改的结果：这时候，再次用mysql空用户名登录，报错
C:\Users\linzm>mysql
ERROR 1045 (28000): Access denied for user 'ODBC'@'localhost' (using password: NO)
