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NORMALIZATION RELATED TO DATABASE MANAGEMENT SYSTEM PDF UPDATE
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Therefore, the details of any faculty member who teaches at least one course can be recorded, but a newly hired faculty member who has not yet been assigned to teach any courses cannot be recorded, except by setting the Course Code to null. For example, each record in a "Faculty and Their Courses" relation might contain a Faculty ID, Faculty Name, Faculty Hire Date, and Course Code. There are circumstances in which certain facts cannot be recorded at all. Specifically, the relation provides conflicting answers to the question of what this particular employee's address is.

If the update is only partially successful – the employee's address is updated on some records but not others – then the relation is left in an inconsistent state.

For example, each record in an "Employees' Skills" relation might contain an Employee ID, Employee Address, and Skill thus a change of address for a particular employee may need to be applied to multiple records (one for each skill). The same information can be expressed on multiple rows therefore updates to the relation may result in logical inconsistencies. When an attempt is made to modify (update, insert into, or delete from) a relation, the following undesirable side-effects may arise in relations that have not been sufficiently normalized: Giddens is lost if they temporarily cease to be assigned to any courses. To make the collection of relations neutral to the query statistics, where these statistics are liable to change as time goes by.Ī deletion anomaly.To make the relational model more informative to users.To reduce the need for restructuring the collection of relations, as new types of data are introduced, and thus increase the life span of application programs.

To free the collection of relations from undesirable insertion, update and deletion dependencies.

The objectives of normalisation beyond 1NF (first normal form) were stated as follows by Codd: ( SQL is an example of such a data sub-language, albeit one that Codd regarded as seriously flawed.

3 Example of a step by step normalizationĪ basic objective of the first normal form defined by Codd in 1970 was to permit data to be queried and manipulated using a "universal data sub-language" grounded in first-order logic.

1.1 Minimize redesign when extending the database structure.

NORMALIZATION RELATED TO DATABASE MANAGEMENT SYSTEM PDF CODE

NORMALIZATION RELATED TO DATABASE MANAGEMENT SYSTEM PDF UPDATE

NORMALIZATION RELATED TO DATABASE MANAGEMENT SYSTEM PDF FREE