mysql 报错ERROR 1820 (HY000): You must reset your password using ALTER USER statement before executing

昨天登录mysql（Server version: 5.7.11） 还是很好的，今天登录后执行任何命令都报下面的错误

[root@service2 ~]# mysql -uroot -p
Enter password: 
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 4
Server version: 5.7.19


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mysql> use mysql
ERROR 1820 (HY000): You must reset your password using ALTER USER statement before executing this statement.
mysql> update user set authentication_string=password('Qaz123$%^') where user='root';
解决办法
1、 修改用户密码

mysql> alter user 'root'@'localhost' identified by 'Qaz123$%^';  

或者       

mysql> set password=password("alter user 'root'@'localhost' identified by 'Qaz123$%^';  ");
2、刷新权限
mysql> flush privileges;