1 - Database Intro

M cheung william tan and carson woo insertion anomaly

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Unformatted text preview: • Is it possible to add a new supplier who has not • Deletion anomaly involves the unintentional deletion supplied any inventory items to the company? supplied any inventory items to the company? of data from table of data from a table. This is not possible because possible because the primary key for the Inventory table is Part Num table is Part Num. The supplier data cannot be added to the table until to the table until the company purchases from thi this supplier. BUSI 335 Copyright © 2009-10 Y.M. Cheung, William Tan and Carson Woo 86 87 Assume that Supplier 27 Supplier 27 provides the company with one item: Part Num item: Part Num 1. If this item is discontinued and deleted from the deleted from the table, the Supplier 27 data will also be deleted be deleted. BUSI 335 Copyright © 2009-10 Y.M. Cheung, William Tan and Carson Woo 88 Accountants Accountants and Data Normalization Normalization The Data Normalization Process Data Normalization Process • Update anomalies can generate conflicting • A process which systematically splits and obsolete database values and obsolete database values. • Insertion anomalies can result in unrecorded transactions and incomplete audit trails transactions and incomplete audit trails. • Deletion anomalies can cause the loss of accounting records and the destruction of accounting records and the destruction of audit trails. • Accountants should understand the data normalization normalization process and be able to determine whether a database is properly normalized normalized. BUSI 335 Copyright © 2009-10 Y.M. Cheung, William Tan and Carson Woo unnormalized complex tables into smaller unnormalized complex tables into smaller tables that meet two conditions: – all nonkey attributes in the table are dependent on nonkey attributes in the table are dependent on the primary key – all nonkey attributes are independent of the other nonkey nonkey attributes • When unnormalized tables are split and unnormalized tables are split and reduced to third normal form, they must then be linked together by foreign keys. 89 BUSI 335 Not all data attributes logically relate to the primary key P...
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