Oracle Physical Design Relation Modeling Oracle Tips by Burleson Consulting

The Data Warehouse Development Life Cycle

Oracle Data Warehouse Design

Entity/Relation Modeling

If we have followed the process for normalization through third normal form,, we will be able to derive an entity/relation model that is essentially free of redundant information (see Figure 4.1). The entity/relation model was first introduced by Professor Emeritus Peter Chen from the University of Louisiana, and it is sometimes called a Chen diagram. In the 15 years since the introduction of this model, many permutations have been created, but the basic principles of entity/relations modeling remain intact.

Figure 4.1 An entity/relation model for Guttbaum’s Grocery.

But is the E/R model for Guttbaum’s Grocery truly free from data redundancy? While the model is free of redundant information, it is impossible to implement the model in a relational database without introducing redundancy to support the data relationships. For example, if Guttbaum’s model was implemented using a pointer-based DBMS, such as IMS, pointers would be used to establish relationships between entities. For relational databases, data columns must be copied as foreign keys to establish data relationships, thereby introducing redundancy.

---

This is an excerpt from "High Performance Data Warehousing", copyright 1997.

If you like Oracle tuning, you may enjoy the book Oracle Tuning: The Definitive Reference , with over 900 pages of BC's favorite tuning tips & scripts.  You can buy it directly from the publisher and save 30%, and get instant access to the code depot of Oracle tuning scripts.