MYSQL：使用UPDATE修改用户名，无法登录

1、创建一个用户test/test

mysql> create user test identified by 'test';
Query OK, 0 rows affected (0.00 sec)

mysql> exit
Bye

2、使用test/test用户登录成功

C:\Users\qxl>mysql -utest -ptest
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 25
Server version: 5.1.28-rc-community MySQL Community Server (GPL)

Type 'help;' or '\h' for help. Type '\c' to clear the buffer.

mysql> exit
Bye

3、使用root用户登录，修改test用户名为newuser

C:\Users\qxl>mysql -uroot -p
Enter password: ****
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 27
Server version: 5.1.28-rc-community MySQL Community Server (GPL)

Type 'help;' or '\h' for help. Type '\c' to clear the buffer.

mysql> update mysql.user set user='newuser' where user='test';
Query OK, 1 row affected (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> exit
Bye

4、使用newuser/test登录失败

C:\Users\qxl>mysql -unewuser -ptest
ERROR 1045 (28000): Access denied for user 'newuser'@'localhost' (using password: YES)