The scenario that you posted about here is a little complex and will require a good deal of custom coding to account for. Essentially you will need to check to see if the item you are adding or updating is set to be featured. If it is then you will need to update all of the items and set the featured to 0 before you insert or update the current record. Then when you insert or update the current record no others will be set to be featured expect the one you are currently working with.