Is it okay if admin's username have the same value of username of another user in database?

I'm confuse about login and register system between user and admin, for example, Admin have the username "andy1234" but the user want to create a username with "andy1234" too. So, should I accept username of admin and username of user can have the same value in my Database? If it can, should I use "unique filtered index" in Mysql ?, because I'm doing with MariaDB.