Joomla Database Prefix
Changing the Joomla database prefix is recommended for each and every Joomla installation.
HOW TO CHANGE JOOMLA DATABASE PREFIX
Upon installation, you have an option to change the database prefixfrom jos_ to what you want. This is all there is to that.
After Installation Joomla Database Prefix Change
After a Joomla site is up and running, changing the Joomla database prefix can be a little more complicated.
To change the database prefix after installation,
1) Login to phpmyadmin.
2) Export the database as text or have it displayed in phpmyadmin. Aftyer it is displayed in phpmyadmin, copy the entire text and paste it into Notepad or Wordpad.
3) Search all text for the prefix and replace all. This will change all desired database prefixes.
You should use the underscore in the search like jos_ because any other words with that string will change; and that could be anything from a menu item to a string in article. For all intensive purposes, a database named with a string that would not be used for any other purpose (i.e. mydbnewz_) would eliminate any naming issues.
4) If your templates have the same name as your database prefix, in part or in whole, you will need to make more changes to either your template names or the templates_menu database table. Renaming them in either situation will help to make the changeover occur.
5) If you use a sef component, you may find that the template routes are incorrect. You must change this, but changing templates names is an easier option. For example, if your template was called ZZZmysite and your database was originally called ZZZmysite (then changed to ZZZnewsite) you may want to change your templates to ZZZnewsite.