Oracle Tips by Burleson

Preaggregation of data

When you pre-summarize data with materialized views, you don’t need to change your SQL!  Oracle has a super-cool feature called query re-write where Oracle will automatically know when your SQL can use a pre-summarized result. 

So, I have my data, and I want to start building my database.  How can I visualize my data and go through the normalization process with out constantly recreating the database?  For this, you want to use the Entity Relation Diagram.

Entity Relation Modeling

Data modeling is a method for developing the structure of the database.  It uses various tools to define the data, relationships, semantics and data consistency requirements.  The Entity Relation Diagram (ERD) is where most designers start when creating and normalizing a database.  An ERD normally starts on paper with a general layout of the database data entities and their relationships. 

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 25 years since the introduction of this model, many permutations have been created, but the basic principles of entity/relations modeling remain intact.

While an E/R model may be 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 a data model was implemented using a pointer-based DBMS, such as IMS, pointers would be used to establish relationships between entities.

At some point, the diagram becomes unwieldy on paper and an ERD tool is used to graphically finish the design.  In a nutshell, the ER diagram shows the data tables, and more importantly, it shows the one-to-many and many-to-many data relationships:

The above book excerpt is from:

Easy Oracle SQL

Get Started Fast writing SQL Reports with SQL*Plus

ISBN 0-9727513-7-8

Col. John Garmany 

http://www.rampant-books.com/book_2005_1_easy_sql.htm