MySQL的用户权限问题

死性不改

编译安装的mysql
使用$mysql 登录进去执行
mysql> create database kk;
ERROR 1044 (42000): Access denied for user ''@'localhost' to database 'kk'
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[wanyu@BanYao ~]$ mysql -uroot -p
Enter password:
ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: NO)
也不行，mysql的root用户密码默认不是空的吗？？
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还有的是运行任何语句都说语法错误：
$mysql
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'select 'dd'' at line 1
mysql>