MySQL 5.7.5 及之前版本：
SET PASSWORD FOR ‘root‘@‘localhost‘ = PASSWORD(‘MyNewPass‘);
MySQL 5.7.6 及之后版本：
ALTER USER ‘root‘@‘localhost‘ IDENTIFIED BY ‘MyNewPass‘;
或者：
UPDATE mysql.user SET authentication_string = PASSWORD(‘MyNewPass‘), password_expired = ‘N‘ WHERE User = ‘root‘ AND Host = ‘localhost‘; FLUSH PRIVILEGES;
原文：http://www.cnblogs.com/agmj117/p/7741968.html