If you know me personally, you probably have a specific name, or nickname, that you associate with me. However, it might not be the same name that others use for me. Here are just a few of the names that I use.
My legal name. However, "David" is a very common name, and it's often confusing when there are other Davids around.
My initials. Primarily used by people in my software/techie circle of friends. It's short, easy to say, and easy to type. I also like the association with databases.
A nickname from college that stuck. No, it's not my middle name, nor does it have any association whatsoever with my legal name. If you're curious, ask me about the story behind this name!
More of an affectionate name, but one that I use nonetheless.
All of these names refer to me, and I don't consider one of them more primary than the others.