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已經設置過密碼,采用如下方法
  mysqladmin -u root password oldpass "newpass"
方法3: 用UPDATE直接編輯user表
  mysql -u root
  mysql> use mysql;
  mysql> UPDATE user SET Password = PASSWORD('newpass') WHERE user = 'root';
  mysql> FLUSH PRIVILEGES;
在丟失root密碼的時候,可以這樣
  mysqld_safe --skip-grant-tables&
  mysql -u root mysql
  mysql> UPDATE user SET password=PASSWORD("new password") WHERE user='root';
  mysql> FLUSH PRIVILEGES;