1 - Database Intro

M cheung william tan and carson woo 78 data model

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Unformatted text preview: tance Letter Student Acceptance Letter BUSI 335 Copyright © 2009-10 Y.M. Cheung, William Tan and Carson Woo 79 BUSI 335 Copyright © 2009-10 Y.M. Cheung, William Tan and Carson Woo 80 Final Final Highline University Data Model Model Data Normalization Normalization • What iis Data Normalization? s Data Normalization? • Why Data Normalization? BUSI 335 Copyright © 2009-10 Y.M. Cheung, William Tan and Carson Woo 81 BUSI 335 User View of Inventory Data View of Inventory Data created based on the information shown above created based on the information shown above. Copyright © 2009-10 Y.M. Cheung, William Tan and Carson Woo 82 Unnormalized Database Table Database Table • A single unnormalized table called Inventory can be BUSI 335 Copyright © 2009-10 Y.M. Cheung, William Tan and Carson Woo 83 • What problems can you identify from this unnormalized unnormalized table? BUSI 335 Copyright © 2009-10 Y.M. Cheung, William Tan and Carson Woo 84 Three Types of Anomalies Three Types of Anomalies Update Anomaly Anomaly • Update anomaly results from data redundancy in an • Unnormalized tables are associated with unnormalized table unnormalized table. three three types of problems, called anomalies. • Insertion Anomaly The supplier’s data attributes data attributes (name, address and tel. number) are repeated in are repeated in every record of inventory item. E.g. What if What if Supplier Number 22’s address is changed? – A new item cannot be added to the table until at it th least one entity uses a particular attribute item. • Deletion Anomaly – If an attribute item used by only one entity is deleted, all information about that attribute item is lost. lost. • Update Anomaly – A modification on an attribute must be made in each of the rows in which the attribute appears. th th BUSI 335 Copyright © 2009-10 Y.M. Cheung, William Tan and Carson Woo 85 BUSI 335 Copyright © 2009-10 Y.M. Cheung, William Tan and Carson Woo Insertion Anomaly Anomaly Deletion Anomaly Anomaly...
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