Chapter 1 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach

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XPLevel 3 Objectives: Identifying and Eliminating Database Anomalies

by Normalizing Data

• Learn the techniques for normalizing data

• Evaluate fields that are used as keys

• Test the database design

Chapter 1 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach

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XPNormalizing the Tables in the Database

• Normalization Design process Goals

• Reduces space required to store data by eliminating duplicate data in database

• Reduces inconsistent data in database by storing data only once

• Reduces chance of deletion update and insertion anomalies

Chapter 1 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach

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XPNormalizing the Tables in the Database (continued)

• Deletion anomaly User deletes data from database Unintentionally deletes only occurrence of data in

database

• Update anomaly Due to redundant data in database User fails to update some records or updates records

erroneously

• Insertion anomaly User cannot add data to database unless preceded by

entry of other data

Chapter 1 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach

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XPNormalizing the Tables in the Database (continued)

• Functional dependency Column in table considered functionally dependent on

another column • If each value in second column associated with exactly

one value in first column

• Partial dependency Field dependent on only part of primary key

• Composite primary key Primary key uses two or more fields to create unique

records in table

Chapter 1 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach

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XPNormalizing the Tables in the Database (continued)

• Determinant Field or collection of fields whose value determines

value in another field Inverse of dependency

• Natural key Primary key that details obvious and innate trait of

record

• Artificial key Field whose sole purpose is to create primary key Usually visible to users

Chapter 1 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach

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XPNormalizing the Tables in the Database (continued)

• Surrogate key Computer-generated primary key Usually invisible to users

Chapter 1 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach

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XPFirst Normal Form

• Repeating group Field contains more than one value

• First normal form 1NF Does not contain any repeating groups

Chapter 1 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach

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XPSecond Normal Form

• 2NF

• Table must be in 1NF

• Must not contain any partial dependencies on composite primary key

• Tables in 1NF and contain primary key with only one field Automatically in 2NF

Chapter 1 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach

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XPThird Normal Form

• 3NF

• Only determinants must be candidate keys

• Candidate key Field or collection of fields that could function as

primary key but was not chosen to do so

• Transitive dependency Occurs between two nonkey fields both dependent on

third field

• Tables in 3NF should not have transitive dependencies

Chapter 1 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach

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XPLevel 3 Summary

• Normal forms First (1NF) Second (2NF) Third (3NF)

Chapter 1 Succeeding in Business with Microsoft Office Access 2003: A Problem-Solving Approach

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XPChapter Summary

• Discovery: Identify existing and missing data Organize data into tables Determine data types for each field

• Table relationships Established through common fields Types

• 1:M• 1:1• M:N

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XPChapter Summary (continued)

• Normalization Reduces duplication and inconsistency Forms:

• 1NF• 2NF• 3NF