How to determine your database prefix
From Joomla! Documentation
There are few methods to determine your database prefix. The recommended method is to view the Global Configuration Database Settings Group from the administrator view of your Joomla! website. There are two other methods also available, but require server access to the files or the database.
Changing your prefix in Global Settings will break your website! If you must change the prefix of your database, it will be a two step process and beyond the scope of this article.
Using the Joomla! Back-end (Super administrators only)
- Log in to the Joomla! backend.
- Go to Global Configuration by clicking the button in the control panel or via the menu (Site > Global Configuration).
- Go to the Server Tab.
- Under Database Settings, look for Database Prefix field. The value you find there is your database prefix.
Look for the yellow warning symbol.
Using Configuration.php (Requires Access to the Site Root)
- Go to the document root and find the configuration.php file.
- Open the file in a text editor.
- Search for the word dbprefix.
- You'll see the line var $dbprefix = 'value'. The value you see here (for example, jos_) is your database prefix.
Using a Database Interface (Requires Access to the Database, e.g. phpMyAdmin for MySQL)
Log into your database using phpMyAdmin. You will need the database username and password - you will have these from when you created the database. (If you do not have the username and password available you can retrieve them from the Joomla! website's configuration.php file - using the $user and $password variables to login.)
When you are connected to the database - look at the name of every table of the website. It will begin with a group of letters and the underscore symbol ('_'). These letters and the underscore is the database prefix for your website. An example prefix looks like this: 'jos_'.
If you have several databases make sure you connect to the database for your Joomla! website - you will find the name in the configuration.php file in the $db variable.