COMMON DATA MODELING PROBLEMS - A Developer's Guide to Data Modeling for SQL Server - page 171

CHAPTER 8
C OMMON D ATA
M ODELING P ROBLEMS
Perfecting a data model is no easy task. To do it correctly, you must balance
the physical limitations of SQL Server 2008 and simultaneously meet the
requirements of your customer's business. Along the way, there are several
pitfalls you may encounter. Many of the problems you will face are quite
common, and you can avoid them by understanding them. In this chapter,
we discuss some of the more common modeling problems and explain how
to identify them, how to fix them if they occur, and how to avoid them
altogether.
Entity Problems
Data models are built around entities, so that is where we start when look-
ing for problems. Some entity problems are obvious, and others are a little
harder to pick up on and fix. We focus on problems surrounding the num-
ber of entities and attributes, and problems that can arise when you don't
pair attributes with an appropriate entity.
Too Few Entities
In the name of a clean, simple, easy-to-use data model, many modelers
create fewer entities than are required. This practice can often lead to a
model that's inflexible and difficult to use.
If you suspect that your model has too few entities, the first thing to
look for is having similar data in the same entity. For example, look at the
original Customers entity for Mountain View's logical model, as shown in
Figure 8.1.
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