help with ad serving

hi there my next project at work is to build an ad server for both image and flash , i am storing each ad entry into a banner_ads table then another table media to store each of the banners into which links to the banner , although in the created admin tool i allow for multiple uploads so a flash file can be uploaded for the banner entry and a animated gif version can also be uploaded for the banner entry , or just an animated gif banner version , ok so when i select for a banner with a start and end date range which is valid and is to be shown on a selected site id i grab the files associated with it which are the flash and image, so in my while loop i end up with to rows of results how would it be possible to display this and how am i able to tell if the banner is a flash file with the animated gif version of if the banner is just an animated gif and display it differently ? let me know thankyou