方法1： 用SET PASSWORD命令

mysql -u root
mysql> SET PASSWORD FOR 'root'@'localhost' = PASSWord('newpass');

方法2：用mysqladmin
mysqladmin -u root password "newpass"
如果root已经设置过密码，采用如下方法
mysqladmin -u root password oldpass "newpass"

方法3： 用UPDATE直接编辑user表
mysql -u root 
mysql> use mysql;
mysql> update user SET Password = PASSWord('newpass') where user = 'root';
mysql> FLUSH PRIVILEGES;


在丢失root密码的时候，可以这样:

mysqld_safe --skip-grant-tables&
mysql -u root mysql
mysql> update user SET password=PASSWord("new password") where user='root';

mysql> FLUSH PRIVILEGES;