Never use your root account and password when running databases. The root account is a privileged account which should only be used for admin procedures.

And also unadvisable to add global MySQL server privileges to those database users who connect to a MySQL database from an application/script (Joomla, Drupal, etc). Better if you setup these users separated to one database with database specific privileges.

You can add users to a MySQL database by using a control panel like phpMyAdmin to easily create or assign database permissions for users.

Launch Phpmyadmin. Click "Privileges" and click "Add a New User" (you can also edit an existing user from the list).

Fill the "Login Information" form, check "None" in the "Database for user" area, don't check/add global privileges for this user just click "Go".

Select the wanted database from the drop-down list.

Add database specific privileges to the previously created user. In the most case you need to add one database user with grant privileges to one database . So "Check All" and click "Go".

Check the user privileges and you are done.