lect7 - 1.264 Lecture 7 Data normalization MIT Bus Company...

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1.264 Lecture 7 Data normalization
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MIT Bus Company Exercise Determine and name entity types Determine cardinality (1:N, N:N) and type (mandatory/optional) of relationships Add identifiers and primary and foreign keys Label relationship phrases Use Visual Paradigm: Create new entities (toolbar) Set attributes and primary keys (properties) Let the relationships fill in the foreign keys Ignore data type (accept integer default) Edit the relationship to be 1-many, 0/1-many if you have time Four exercises follow: do them all in the same diagram, but they are separate exercises Name the entities differently in each exercise (e.g., Vehicle1, Vehicle2)
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MIT Bus Company Bus company employs mechanics to maintain vehicles. Each mechanic usually assigned to many vehicles. Vehicle always assigned to 1 mechanic.
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MIT Bus Company Bus company employs mechanics to maintain vehicles. Each mechanic usually assigned to many vehicles. Vehicle always assigned to 1 mechanic.
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MIT Bus Company Bus company has several garages. A garage may contain many bays. A bay must be in a garage.
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MIT Bus Company Bus company has several garages. A garage may contain many bays. A bay must be in a garage.
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MIT Bus Company Garage employs managers to monitor vehicle availability and repair costs. Each manager is assigned at least 1 and usually many vehicles. A vehicle may or may not have a manager responsible.
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MIT Bus Company Garage employs managers to monitor vehicle availability and repair costs. Each manager is assigned at least 1 and usually many vehicles. A vehicle may or may not have a manager responsible.
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MIT Bus Company Garage maintains a list of specialized repair personnel who are used as necessary. A specialist may work on many vehicles. A vehicle may or may not be repaired by a specialist.
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MIT Bus Company Garage maintains a list of specialized repair personnel who are used as necessary. A specialist may work on many vehicles. A vehicle may or may not be repaired by a specialist.
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Normalization rules Prevent update anomalies (mistakes) and data inconsistencies Degrade performance, usually only slightly More impact on reads, where several rows vs one are read Little impact on writes, which tend to be the bottleneck anyway Denormalization is common on read-only databases and in report generation or data warehouses. You can’t have update anomalies if you don’t do updates! Your homework 4 initial data is not normalized. Homeworks
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This note was uploaded on 12/06/2011 for the course ESD 1.264j taught by Professor Georgekocur during the Fall '06 term at MIT.

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lect7 - 1.264 Lecture 7 Data normalization MIT Bus Company...

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