Tuning the Schema - Professional SQL Server 2005 Performance Tuning - page 189

Tuning the Schema
A key component in creating a high-performance database or improving one that is performing
inadequately lies in the schema. The schema refers to both the general and specific design of a
database. General aspects include items such as normalization and database style (OLTP, OLAP).
Specific aspects include items such as data types, foreign key relationships, table definitions, and
so on. This chapter serves as a guide, describing the techniques and methodologies addressing
both areas.
Data Quality
The quality of data simply means how dependable the data is. Obviously, you want your
organization's data to be as dependable as possible. This section covers topics of normalization,
defining columns, stored procedures, and triggers. All of these areas have a great impact on
dependability of data.
Normalization
This is a term you've probably heard before, but may not fully understand. Exacerbating this misun-
derstanding are textbooks and references that tend toward heavy use of jargon and
mathematical symbology. Therefore, clear explanations of the issues that normalization addresses
and the techniques used are necessary. First, the primary problems addressed concern data qual-
ity. Data inconsistencies and anomalies lead to poor data quality. In order to eliminate or at least
minimize that situation, a proven process of reorganization is needed. Edgar F. Codd, the pioneer
of relational database methodology, first described this process, which he defined as normalization.
He described it as a method in which non-simple domains are decomposed to the point that the
elements are atomic values (no further decomposition is possible).
The best way to understand these issues is with an example. A data set is presented. Next, the
anomalies that can occur on that set are described. Finally, the data set will be reorganized using
proven normalization rules.