The following error appears while trying to login to MySQL at the prompt on Plesk from root user:
ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: NO)
This is because Plesk doesn't allow root user to login to MySQL. Use admin user instead. Plesk stores the admin password in /etc/psa/.psa.shadow file. You can supply the admin password while connecting or pass the password directly as: