Chapter 5 - Chapter5:Normalization What is Normalization...

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Chapter 5: Normalization What is Normalization? Why is its done? The normal forms 1NF, 2NF, 3NF, BCNF, 4NF Transforming normal forms E-R modeling and normalization Denormalization Database Tables and Normalization Normalization is a process for assigning attributes to entities to: Reduce data redundancies o Help eliminate data anomalies Produce controlled redundancies to link tables No information is lost in normalization Result will be a database that can produce the same information as the original Normalization Process Normalizatin works through a series of stages called normal forms: First Normal form (1NF) Second normal form (2NF) Third normal form (3NF) etc (4th and 5th) 2NF is better than 1NF; 3NF is better than 2NF For most business database design purposes, 3NF is highest we need to go in the normalization process Highest level of normalization is not always most desirable The Need for Normalization Example: company that manages building projects Charges its clients by billing hours spent on each contract Hourly billing rate is dependent on employee’s position Periodically, a report is generated that contains information as follows Sample Report
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Table derived form Above
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The Need for Normalization Structure of data set in Figure 5.1 does not handle data very well The table structure appears to work; report is generated with ease Unfortunately, the report may yield different results, depending on what data anomaly has occurred Issues Table entries invite data inconsistencies Table displays potential data anomalies o Update: Modifying JOB_CLASS o Insertion: New Employee must be assigned project o Deletion: If employee deleted, other vital data lost: if emp 103 leaves lose info on Elect Engineers Repeating Group
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Repeating group Derives its name from the fact that a group of multiple (related) entries can exist
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This note was uploaded on 10/25/2010 for the course CMPN SEM4 taught by Professor Thakur during the Spring '07 term at University of Mumbai.

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Chapter 5 - Chapter5:Normalization What is Normalization...

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