Mac-Auth with MySQL

Hi All, I am currently running radius with Mysql backend. I am using PAP and like to add the Mac-Auth. What files I need to tweak? I have looked at the http://wiki.freeradius.org/Mac-Auth but got confused with the 'raddb/modules/file' and specially 'raddb/authorized_macs'. My question is why do I need to specify the MAC in file instead of database? Thanks Deepak