Entity-relationship diagrams (ERDs) are an important tool in good database design. Small databases can usually be easily created from a few scripts and implemented directly without drawing things out at all. The larger your database gets, however, the faster it becomes very problematic to just do things "in your head." ERDs solve a ton of problems because they allow you to quickly visualize and understand both the entities and their relationships.
For this book, I've decided to do things somewhat in reverse of how I've done things before. SQL Server includes a very basic diagramming tool that you can use as a starting point for building rudimentary ERDs. Unfortunately, it employs a proprietary diagramming methodology that does not look remotely like any standard I'm aware of out there. In addition, it does not allow for the use of logical modeling — something I consider a rather important concept. Therefore, I'm going to start off talking about the more standard diagramming methodologies first — later in the chapter you will look at SQL Server's built in tools and how to use them.
There are two reasonably common diagramming paradigms — IE and IDEF1X. You'll find both of these in widespread use, but I'm going to limit things here to a once over of the basics of IE (also called Information Engineering). For the record, IDEF1X is a perfectly good diagramming paradigm, and was first put forth by the U.S. Air Force. IE (again, Information Engineering — not Internet ...