Data Redundancy Revisited NIK UiTM 34 Data redundancy leads to data anomalies

Data redundancy revisited nik uitm 34 data redundancy

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Data Redundancy Revisited NIK UiTM 34 Data redundancy leads to data anomalies Can destroy the effectiveness of the database Foreign keys Control data redundancies by using common attributes shared by tables Crucial to exercising data redundancy control Sometimes, data redundancy is necessary
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35 NIK UiTM
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36 Data Redundancy Revisited (continued) NIK UiTM
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Indexes NIK UiTM 37 Orderly arrangement to logically access rows in a table Index key Index’s reference point Points to data location identified by the key Unique index Index in which the index key can have only one pointer value (row) associated with it Each index is associated with only one table
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NIK UiTM 38
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Codd’s Relational Database Rules NIK UiTM 39 In 1985, Codd published a list of 12 rules to define a relational database system Products marketed as “relational” that did not meet minimum relational standards Even dominant database vendors do not fully support all 12 rules
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40 NIK UiTM Codd’s Relational Database Rules (Continued)
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Summary NIK UiTM 41 Tables are basic building blocks of a relational database Keys are central to the use of relational tables Keys define functional dependencies Superkey Candidate key Primary key Secondary key Foreign key
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Summary (cont’d.) NIK UiTM 42 Each table row must have a primary key that uniquely identifies all attributes Tables are linked by common attributes Good design begins by identifying entities, attributes, and relationships 1:1, 1:M, M:N
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NIK UiTM 43
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NIK UiTM 44 c. Create ERD
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NIK UiTM 45
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Exercise NIK UiTM 46 Based on text books: Refer Figure p4.1 (page 139), answer question 1,2,3,8,9 Refer Figure p4.10(page140), answer question 10,13,14,15 and 16.
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