Beginning Microsoft SQL Server 2008 ... - S3 Tech Training

Chapter 8: Being Normal: Normalization and Other Basic Design Issues
OK, so are you storing information on whether your vendor is a corporation or not? You had better be
if you are subject to U.S. tax law (1099 reporting). So you turn around and say that you can handle
that, and the customer replies, “Great! Can you print that out along with their address as of the end of
the year?”
Oops — I’m betting that you don’t have past addresses, or at the very least, aren’t storing the date
that the address changed. In short, you never know what a user of your system is going to ask for —
try and make sure you have it. Just keep in mind that you don’t want to be moving unnecessary
amounts of data up and down your network wire (see my comments on choosing a data type). If
you’re storing the data just for posterity, then make sure you don’t put it in any of your application’s
SELECT statements if it isn’t needed (actually, this should be your policy regardless of why you’re
storing the data).
Drawing Up a Quick Example
Let’s walk quickly through a process of designing the invoicing database that we’ve already started with
during our section on normalization. For the most part, we’re going to just be applying the diagramming
tools to what we’ve already designed, but we’ll also toss in a few new issues to show how they affect
our design.
Creating the Database
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If you think that there may be legal ramifications either way (both in keeping it and
in getting rid of it), consult your attorney. Sometimes you’re legally obligated to
keep data a certain amount of time; other times it’s best to get rid of information as
soon as legally possible.
Unlike a lot of the third-party diagramming tools out there, the SQL Server diagramming tools will not
create the database for you — you have to already have it created in order to get as far as having the diagram
available to work with.
We’re not going to be playing with any data to speak of, so just create a small database called Invoice. I’ll
go ahead and use the dialog in the Management Studio for the sake of this example.
After right-clicking on the Databases node of my server and selecting New Database, I enter information
in for a database called Invoice that is set up as 3MB in size.
Since we’ve already had a chapter on creating databases (and for the sake of brevity), I’m just going to
accept the defaults on all the other options, as shown in Figure 8-23.