ITM 500 Lecture Notes - Lecture 11: Compound Key, Unique Key, Data Redundancy

• School: Ryerson University
• Department: Information Technology Management
• Course: ITM 500
• Professor: Raymond Moss

Document Summary

A major objective of a relational database design is to ensure data consistency and integrity. A way to achieve this is to eliminate data duplication from the design. Another term for this duplication is data redundancy. Normalization is a standard set of rules and processes, applied to the data, to eliminate redundancy. The consequence of data redundancy is the presence of modification anomalies. An anomaly is an unexpected side effect. These can occur when transactions to add, change or delete data are applied to un- normalized data. The outcome can be unintended data changes that can cause integrity problems. To eliminate anomalies, the design must essentially strive for one fact in one place. Using a single integrated example, this tutorial will step through the basic forms (rules of normalization. The final results should be a set of fully normalized relations. Data doesn"t exist in a vacuum and the same data can appear in different structures.