[root@localhost mysql]# mysql -u root -p
Enter password:
ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: NO)
解决方法：
方法一：
# /etc/init.d/mysql stop
# mysqld_safe --user=mysql --skip-grant-tables --skip-networking &
# mysql -u root mysql
mysql> UPDATE user SET Password=PASSWORD(’newpassword’) where USER=’root’;
mysql> FLUSH PRIVILEGES;
mysql> quit
# /etc/init.d/mysql restart
# mysql -uroot -p
Enter password: <输入新设的密码newpassword>
mysql>SET PASSWORD = PASSWORD('123456')
上面这一句必须要执行，要不然会出现“ERROR 1820 (HY000): You must SET PASSWORD before executing this statement” 的错误