Custom WordPress feed xml (from mysql)

I need a system should be connected to WordPress which could get datas from MySQL and compact into an XML file. The WordPress has more than 200.000 posts so it should work without any problem. We would like it to run with CRON once each day. Data: WordPress posts: 200.000!! More Custom Fields Cotum post type Example feed: <?xml version="1.0" encoding="utf-8"?> <listings> <listing> <record_id>POST_ID</record_id> <title><![CDATA[POST-TITLE]]></title> <url>POST_URL</url> <category><![CDATA[POST-CATEGORY 1]]></category> <Job_category><![POST-CATEGORY 2]]></Job_category> <city>COSTUM FIELDS 1</city> <Experience>COSTUM FIELDS 2</Experience> <description><![CDATA[Test Ad13]]></description> <listing_time>CREAT DATE(FORMAT: 2010-11-03 10:55)</listing_time> <expire_time>CREAT DATE+10days</expire_time> </listing> </listings>