1、刷新

flush privileges;

2、设置root密码（5.7）

UPDATE mysql.user SET authentication_string = PASSWORD('密码') where User = 'root';
flush privileges;

设置成功后登陆报错
You must reset your password using ALTER USER statement before executing this statement.

SET PASSWORD = PASSWORD('密码');
ALTER USER 'root'@'localhost' PASSWORD EXPIRE NEVER;
flush privileges;

3、创建用户(5.7)

create user 'user'@'localhost' identified by '密码';

授权

grant all privileges on DBNAME.* to 'user'@'localhost' identified by '密码';