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ICS 321 Fall 2009 Schema Refinement & Normal Forms

ICS 321 Fall 2009 Schema Refinement & Normal Forms. Asst. Prof. Lipyeow Lim Information & Computer Science Department University of Hawaii at Manoa. The Problem with Redundancy. Hourly_Emps. Suppose hourly wages are determined by rating ( this is an eg of functional dependency )

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ICS 321 Fall 2009 Schema Refinement & Normal Forms

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  1. ICS 321 Fall 2009Schema Refinement & Normal Forms Asst. Prof. Lipyeow Lim Information & Computer Science Department University of Hawaii at Manoa Lipyeow Lim -- University of Hawaii at Manoa

  2. The Problem with Redundancy Hourly_Emps • Suppose hourly wages are determined by rating ( this is an eg of functional dependency) • Redundant storage : (8,10) stored multiple times • Update anomaly : change hourly wages in row 1 • Insertion anomaly : requires knowing hourly wages for the rating • Deletion anomaly : deleting all (8,10) loses info Lipyeow Lim -- University of Hawaii at Manoa

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