Assignment1a - Page 28: Exercise 1.9 What is the difference...

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Page 28: Exercise 1.9 What is the difference between controlled and uncontrolled redundancy? Illustrate with examples. Redundancy occurs when the storage of the same data occurs in multiple locations in the database. With uncontrolled redundancy, many issues can occur including inconsistent data such as multiple methods of data structure such as order of birth date information, waste of storage space and the duplication of effort of inputting data. The difference between controlled redundancy and uncontrolled redundancy is with controlled redundancy, methods can be used to combine data that is input automatically. An example of this is when you want to retrieve a record with data already concatenated such as with database checking. Such may be the case of a student ID being repeated along with a student name when multiple courses are accounted for in the student record as shown in figure 1.6 on page 18 of the text. This shows how the Student_number is stored multiple times and is verified for consistent data. This is used to ensure the consistency of the data. The Database Management System should be designed with automatic enforcement of data checking such as ensuring the Student_number and Student_name are consistent otherwise the redundancy would not be controlled. In the example of 1.6, this is shown by the error of
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This note was uploaded on 09/07/2011 for the course MIS unknown taught by Professor Unknown during the Fall '09 term at New York Institute of Technology-Westbury.

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Assignment1a - Page 28: Exercise 1.9 What is the difference...

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