You have an error in your SQL syntax； check the manual thatcorresponds to your

报错：

ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that
corresponds to your MySQL server version for the right syntax to use near '('123
456') where user='root'' at line 1

看过很多方法： 

修改密码：

方法1：无效

 set password for 用户名@localhost=password('新密码');

方法2：无效

set password =password('你的密码');
flush privileges;

方法3：有效！！！

       ALTER USER 'root'@'localhost' IDENTIFIED BY 'root';