Manual:$wgDBprefix

From MediaWiki.org

Database settings: $wgDBprefix
Table name prefix.
Introduced in version:	1.4.0
Removed in version:	still in use
Allowed Values:	(string)
Default Value:

Other settings: Alphabetical | By Function

[edit] Details

Table name prefix. If you only have access to a single database and wish to install more than one version of MediaWiki, or have other applications that also use the database, you can give the table names a unique prefix to stop any naming conflicts or confusion.

For example, if you use the prefix 'wiki_' then the table 'page' will be named 'wiki_page' instead.

You need to set this at the time of initial configuration, or manually change the table names at a later date. Changing this setting does not automatically update the names of the tables in your database.

This setting is not used if your database is Postgres: instead, schemas are used (see $wgDBmwschema).