方法0：使用GRANT语句
mysql>grant all on *.* to 'root'@'localhost' IDENTIFIED BY 'newpassword' with grant option ;
mysql>grant all on *.* to 'root'@'%' IDENTIFIED BY 'newpassword' with grant option ;
mysql>grant all on *.* to 'root'@'192.168.1.%' IDENTIFIED BY 'newpassword' with grant option ;
mysql>flush privileges;
方法1： 用SET PASSWORD命令
mysql -u root
mysql> SET PASSWORD FOR 'root'@'localhost' = PASSWORD('newpassword');
方法2：用mysqladmin
mysqladmin -u root password "newpassword"
如果root已经设置过密码，采用如下方法
mysqladmin -u root password oldpass "newpassword"
方法3： 用UPDATE直接编辑user表
mysql -u root
mysql> use mysql;
mysql> UPDATE user SET Password = PASSWORD('newpassword') WHERE user = 'root';
mysql> FLUSH PRIVILEGES;
方法4：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("newpassword") WHERE user='root';
mysql> FLUSH PRIVILEGES;