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Normalisation
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Assignment One: Normalising data Normalisation is a bottom-up approach to database design that begins by examining the relationships between the attributes that in turn make up the database. For this example of normalising data we are going to use data from AllRight Accounting which is a firm that stores data about their customers various policies with other companies. The forms that we are extracting the data from are standard forms used by AlRight Accounting to receive the necessary information on their customers. Here the user fills in a form with details such as Personnel Details, Policy Details, and Company Details. Aaron’s Accounting Client Number: CN 34 Policy Number: PN 12 Full Name: Karen Hatfield Policy Description: Covers holder for full Dental treatment Monthly Debt: £50 Company Number: CN 100 Policy Start: 1- Sep - 99 Company Name: Dave’s Dental Policy Expire: 1- Sep - 00 Source of data: Standard AllRight Accounting customer information form Before we move to First Normal Form (1NF) we show how the data looks from the outset. This is called Unnormalised form (UNF). Unnormalised Form (UNF) A table containing one or more repeating groups customerPolicy (cliebtNo, cName, policyNo, pDesc, pStart, pExpire, mDebt, companyNo, cName) Table Format: ClientRental clientNo cName policyNo pDesc pStart pExpire mDebt companyNo cName CN34 Karen Hatfield PN12PN15 Covers holder for full dental treatmentCovers holder for full home insurance 1 Sep 991 Aug 99 1 Sep 001 Aug 00 £50£60 CN100CN110 Dave’s DentalHomes Cover CN44 Simon Hauss PN12PN20PN15 Covers holder for full dental treatmentCovers holder for full car insuranceCovers holder for full home insurance 12Oct 012 Dec 0112Jan 01 12Oct 022 Dec 0212Jan 02 £50£75£60 CN100CN115CN110 Dave’s DentalCareful CarsHomes Cover First Normal Form (1NF) A relation in which the intersection of each row and column contains one and only one value.
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