Can't access mysql

[MrsBaty]

When I open the command prompt, I type: MySQL -u root;
Then: use MySQL;
I get the error: access denied for user ' '@'localhost' to database 'mysql'
I have never had xampp on this computer & have never had a chance to set up a password. Any suggestions?
*I used xampp on my old computer, Windows 8. This new computer has Windows 10 & MariaDB. Could commands be different or am I doing something wrong?

[Altrea]

Did you change the host of user root from localhost to Any (%)?
Or did you delete the user root@localhost?