Fall08-NF-Lec3

# Fall08-NF-Lec3 - A SIMPLE GUIDE TO FIVE NORMAL FORMS (See...

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09/27/09 Prof. Ghandeharizadeh 1 A SIMPLE GUIDE TO FIVE NORMAL FORMS (See the next slide for required reading)

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09/27/09 Prof. Ghandeharizadeh 2 READING This lecture is based on a seminal paper by William Kent, see William Kent, A simple guide to five normal forms in relational database theory, Communications of the ACM, Volume 26, Number 2, pages 120-125, February 1983. All USC students should download this paper from the ACM Digital Library Portal.
09/27/09 Prof. Ghandeharizadeh 3 A SIMPLE GUIDE TO FIVE NORMAL FORMS Given an application, how to structure the tables that support this application? Solution: Use the five normal forms as guidelines. Why is this important? If one is not careful then: 1. Information might be duplicated, resulting in: update anomalies, and data inconsistencies. 2. Loss of information attribute = field First normal form: all occurrences of a record type must contain the same number of fields. Example: Emp(SS#, name, age, salary, dno) is a relation with five attributes. All tuples/records of this table have five attributes. Second and third normal forms: A non-key attribute is a fact about the key, the whole key and nothing but the key. Key is defined as a set of one or more attributes which, taken collectively, allow us to uniquely identify one record from the others in a table.

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09/27/09 Prof. Ghandeharizadeh 4 A SIMPLE GUIDE TO FIVE NORMAL FORMS (Cont…) The second normal form is violated when a non-key field is a fact about a subset of a key. This circumstance arises when the key is composite. PART WAREHOUSE QUANTITY WAREHOUSE-ADDRESS …… key ………….
09/27/09 Prof. Ghandeharizadeh 5 A SIMPLE GUIDE TO FIVE NORMAL FORMS (Cont…) Limitations: 1. Warehouse address is repeated in every record (every part) 2. If the address of a warehouse changes, many records must be updated

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## This note was uploaded on 01/11/2009 for the course CSCI 485 taught by Professor Ghandeharizadeh during the Fall '08 term at USC.

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Fall08-NF-Lec3 - A SIMPLE GUIDE TO FIVE NORMAL FORMS (See...

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