iRule to access database

iRules have Data Groups -- internal lists that you can look up values in. If you are talking about an external database like MySQL or the like, you can't query real-time but you could hack up a method of loading database values into a data group automatically. Picture this -- set up a cron job to request a web page through the BIG-IP every so often. That web page has a list of the database values. An iRule parses that page and stores it in a Data Group for later use by the iRules in real-time.