As more and more of our applications move into "the cloud", multi-tenancy has become a pretty big thing these days. In a nutshell, "multi-tenancy" means handling multiple customers data using, say, a single server. This concept scales, of course, to clusters, etc., but the concept is the same: a bunch of people’s data all mixed together in one big bucket. The problem, then, for the development team is isolating one customer’s data from another’s, disallowing, for example, the viewing or editing of another customer’s information. There are a myriad of ways to accomplish this, but I’d like to discuss here a way to accomplish this using a single database.