use mysql;
update user set password=‘123456‘ where user=‘root‘; //报unknown column password错误
update mysql.user set authentication_string=password(‘123456‘) where user=‘root‘; //修改root用户密码，密码字段为authentication_string
FLUSH PRIVILEGES; //刷新缓存
原文：http://www.cnblogs.com/sunflower627/p/7471850.html