Boyce-Codd Normal Form - Database Design - Lecture Slides, Slides for DBMS (Database Management Systems). English and Foreign Languages University

DBMS (Database Management Systems)

Description: These lecture slide are very easy to understand and very helpful to built a concept about the foundation of computers and Database Design.The key points in these slide are:Boyce-Codd Normal Form, Database Normalization, Normal Forms, Deletion Anomalies, First Normal Form, Eliminate Repeating Groups, Eliminate Redundant Data, Non-Key Columns, Non-Key Attributes, Third Normal Form
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Boyce-Codd Normal Form

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Overview

• 1NF, 2NF, and 3NF • BCNF • Conclusion

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Database Normalization

• Each datum in the database should represented once.

• Purpose is to eliminate update, insert, and deletion anomalies.

• Normal Forms are increasingly strict subset of 1NF.

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First Normal Form

• Eliminate Repeating Groups • Require uniquely identified rows

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First Normal form

• 1 girl per row • 2 Pamelas are uniquely identifiable.

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Second Normal Form

• Eliminate Redundant Data

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Second Normal Form

• Non-key columns are dependent on all columns of the primary key.

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2NF/3NF

• A Relation without non-key attributes is 2NF and 3NF.

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Third Normal Form

• Eliminate Columns Not Dependent On Key • i.e. if a column is in a relation, then it must be

dependent on the key.

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Third Normal Form

• Move non-key-dependent attributes to a new table.

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Boyce-Codd Normal Form (BCNF)

• 3NF, but… • All functional dependencies imply the only

whole key. • "The key, the whole key, and nothing but

the key, so help me Codd."

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Identifying (non)BCNF

• A Relation can be 3NF and not BCNF if: – There are multiple candidate keys – The keys are composed of multiple attributes – There are common attributes between the keys.

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Example of 3NF and BCNF

Given: R(A,B,C,D,E) AB –> C AB –> D AB –> E DE –> C DE –> A DE –> B With the key AB

• Holds true for 3NF – All left hands of

functional dependencies are candidate keys.

• Breaks for BCNF – There exist

dependencies between candidate keys.

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Summary

• BCNF if: – No dependencies

between candidate keys. – 3NF

• 3NF – No attributes dependent

on non-keys. – 2NF

• Attributes dependent on all parts of the key

• 1NF – No repeating groups – Each row uniquely

identifiable.

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