On Developer Drive today there's a new post (the first in a series) from Gerald Hanks about building an ad tracker in PHP. In this first part he sets up some of the background - the database that will hold the tracker information.

Banner ads for services related to the web site owner’s industry allow customers to view products that tie into the site owner’s core business. In exchange, the web site owner can charge the banner ad owner for every impression (banner ad appearance) or click-through (when a user clicks the banner ad). In order to build a banner ad management system, we must first create the database tables that will hold the ad information, the client data and the activity schedule for each ad.

He includes the SQL you'll need to create a few tables - the tracking table for the ads themselves (their metadata), the clients table to handle the groups wanting the ads and the activity table to track views and click-throughs.