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

Chapter 8: Being Normal: Normalization and Other Basic Design Issues
Note that, for either example, the implementation of referential integrity is the same — each of the base
tables (the tables that hold the underlying data and have the many-to-many relationship) has a one-to-many
relationship with the associate table. This can be done via either a trigger or a FOREIGN KEY constraint.
Diagramming
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.
Fortunately, SQL Server includes a very basic diagramming tool that you can use as a starting point for
building rudimentary ERDs.
Before the first time I wrote this topic, I debated for a long while about how I wanted to handle this. On
one hand, serious ER diagramming is usually done with an application that is specifically designed to
be an ER diagramming tool. These tools almost always support at least one of a couple of industry standard
diagramming methods. Even some of the more mass-market diagramming tools — such as Visio —
support a couple of ERD methodologies. SQL Server has an ERD tool built in, and therein lies the problem.
The tools that are included with SQL Server 2008 are a variation on a toolset and diagramming
methodology that Microsoft has used in a number of tools for many years now. The problem is that they do
not compete with any ERD standard that I’ve seen anywhere else. As I’ve done every time I’ve written on
this topic, I’ve decided to stick with what I know you have — the built-in tools. I do, however, encourage
you to examine the commercially available ERD tools out there to see the rich things that they offer to
simplify your database design efforts.
You can open up SQL Server’s built-in tools by navigating to the Diagrams node of the database you
want to build a diagram for (expand your server first, then the database). Some of what we are going to
see you’ll find familiar — some of the dialogs are the same as we saw in Chapter 5 when we were creating
tables.
The SQL Server diagramming tools don’t give you all that many options, so you’ll find that you’ll get to
know them fairly quickly. Indeed, if you’re familiar with the relationship editor in Access, then much of
the SQL Server tools will seem very familiar.
Try It Out Diagramming
Let’s start by creating our first diagram. You can create your new diagram by right-clicking the Diagrams
node underneath the AdventureWorks2008 database and choosing the New Database Diagram
option.
As we saw back in Chapter 5, you may (if it’s the first time you’ve tried to create a diagram) see a dialog
come up warning you that some of the objects needed to support diagramming aren’t in the database
and asking if you want to create them — choose Yes.
SQL Server starts us out with the same Add Table dialog (see Figure 8-7) we saw in Chapter 5 — the
only thing different is the tables listed.
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