3024-Chap11 - 11. NORMALIZATION OF RELATIONAL SCHEMA When...

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Unformatted text preview: 11. NORMALIZATION OF RELATIONAL SCHEMA When developing a relational schema, our goal of course is to have a good database design. What do e mean by this? we mean by this? Each attribute and schema should have a simple eaning. meaning. edundant values should be controlled Redundant values should be controlled. 2010 John P. Shewchuk ISE 3024 Course Notes 11 1 we start with a good E- model and properly translate If we start with a good E R model and properly translate it, we will obtain a relational schema (set of tables) which addresses these objectives to a good extent. In many cases, however, this procedure is NOT followed: conceptual modeling not done legacy system tables developed based upon sample documents or prior system. In such cases, no guarantee of a good database 2010 John P. Shewchuk ISE 3024 Course Notes 11 2 design, so a process called normalization is performed. ormalization a structured process for identifying Normalization is a structured process for identifying problems in a table structure and removing them. Once a set of tables has been normalized , we are confident that it will provide a good database design. his chapter describes how normalization is performed This chapter describes how normalization is performed. 2010 John P. Shewchuk ISE 3024 Course Notes 11 3 11.1 Redundancy and Anomalies in Relational Schema edundancy = repetition of information. Redundancy repetition of information. Initial Books table (p. 8-6 ): title , author , publisher , year , ISBN and price same for every book of the same title. Every copy of this data is redundant information. Result: wasted time, effort, space. More serious problem, however: anomalous behavior . 2010 John P. Shewchuk ISE 3024 Course Notes 11 4 Types of anomalous behavior: i) Update Anomaly update of data results in inconsistency. book Id title author publisher ISBN year price 12 Star Wars: Jedi Trial Dan Cragg Random House 0-3454-6115-0 2005 $6.99 27 Band of Brothers Stephen Ambrose Simon & Schuster 0-7432-2454-X 2001 $17.82 9 Circle of Friends Maeve Binchy Dell Publishing 0-4402-1126-3 1995 $7.99 7 I A B ttl i h l S k i W 948 636 999 7 50 37 Message In A Bottle Nicholas Sparks Time Warner 1-5948-3636-1 1999 $7.50 23 The Long Road Home Danielle Steel Dell Publishing 0-4402-4344-0 2006 $14.99 4 Star Wars: Jedi Trial Dan Cragg Random House 0-3454-6115-0 2005 $8.99 18 Beyond Valor Patrick ODonnell imon & Schuster- 848- 385- 2001 8.99 8 eyo d V o c O o e S o & S c u s e 0 68 8 7385 0 00 $8.99 32 Curious George Margret and H.A. Rey Houghton Mifflin 0-3951-5023-X 1973 $14.00 17 Beyond Valor Patrick ODonnell Simon & Schuster 0-6848-7385-0 2001 $8.99 2010 John P. Shewchuk ISE 3024 Course Notes 11 5 Update Anomaly ii) Insertion Anomaly adding a new record results in an inconsistency....
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This note was uploaded on 02/14/2010 for the course ISE 3024 taught by Professor Staff during the Spring '08 term at Virginia Tech.

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3024-Chap11 - 11. NORMALIZATION OF RELATIONAL SCHEMA When...

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