Editing Data warehouse (section)

====Normalized approach====
In the normalized approach, the data in the warehouse are stored following, to a degree, [[database normalization]] rules. Normalized relational database tables are grouped into ''subject areas'' (for example, customers, products and finance). When used in large enterprises, the result is dozens of tables linked by a web of joins.(Kimball, Ralph 2008).

The main advantage of this approach is that it is straightforward to add information into the database. Disadvantages include that, because of the large number of tables, it can be difficult for users to join data from different sources into meaningful information and access the information without a precise understanding of the date sources and the [[data structure]] of the data warehouse.

Both normalized and dimensional models can be represented in entity–relationship diagrams because both contain joined relational tables. The difference between them is the degree of normalization. These approaches are not mutually exclusive, and there are other approaches. Dimensional approaches can involve normalizing data to a degree (Kimball, Ralph 2008).

In ''Information-Driven Business'',<ref>{{cite book|last=Hillard|first=Robert|title=Information-Driven Business|year=2010|publisher=Wiley|isbn=978-0-470-62577-4}}</ref> [[Robert Hillard (writer)|Robert Hillard]] compares the two approaches based on the information needs of the business problem. He concludes that normalized models hold far more information than their dimensional equivalents (even when the same fields are used in both models) but at the cost of usability. The technique measures information quantity in terms of [[Entropy (information theory)|information entropy]] and usability in terms of the Small Worlds data transformation measure.<ref>{{cite web|url=http://mike2.openmethodology.org/wiki/Small_Worlds_Data_Transformation_Measure |title=Information Theory & Business Intelligence Strategy - Small Worlds Data Transformation Measure - MIKE2.0, the open source methodology for Information Development |publisher=Mike2.openmethodology.org |access-date=2013-06-14}}</ref>