If you can write a script to get data from mysql, you can get it into Splunk.
The usual way might be to use a shell script calling the mysql interpreter with your desired SELECT statement, returning the rows to STDOUT. Splunk would then index the data being output by the script. Inspecting the database directly from a Splunk script might be just a bit trickier, as I don't know whether a database connector for mysql is included in the Splunk Python library.
This is my favorite app: http://splunk-base.splunk.com/apps/50803/dbx-sql-database-extension. No forwarder required and simple to use. You can do lookups, browse databases, update Splunk indexes from a database, and update the database from Splunk. You should definitely check it out!
As of right now (Oct 3 2012) this app is not downloadable. however, a less rich app (that requires a bit more work) is http://splunk-base.splunk.com/apps/27105/jdbc-scripted-input
It is possible to use a Splunk Forwarder to send data from mysql, but it involves a scripted input. Input configurations are found here: http://docs.splunk.com/Documentation/Splunk/latest/Admin/Inputsconf
. I would call a perl or python script and use that to pull in the data.
Example: http://www.tutorialspoint.com/python/python_database_access.htm
If you can write a script to get data from mysql, you can get it into Splunk.
The usual way might be to use a shell script calling the mysql interpreter with your desired SELECT statement, returning the rows to STDOUT. Splunk would then index the data being output by the script. Inspecting the database directly from a Splunk script might be just a bit trickier, as I don't know whether a database connector for mysql is included in the Splunk Python library.
http://splunk-base.splunk.com/apps/50803/dbx-sql-database-extension
http://splunk-base.splunk.com/apps/27105/jdbc-scripted-input
are apps that will do this for you.