27-12-2012, 06:24 PM
Basics of Normalization resolved with Examples
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Normalization Resolved
Normalization is one of the favourite topics of interviewee. It does not matter whether you have mentioned DBMS in your resume or not .This question is going to come and the funny part is that all of us know what is normalization? What are the different types of normalization? So when this question on being asked the interviewer who have already prepared for it start with the history of normalisation and end with the geography of normalization but when the next question for which they have not prepared i.e apply normalization in real case scenario.
Now here comes the real part of normalization and just because of not proper concepts, people end up confusing themselves. So the idea is to not only to get familiar with normalization but also how to apply it in real time scenario.
What is Normalization?
Database designed based on ER model may have some amount of inconsistency, ambiguity and redundancy. To resolve these issues some amount of refinement is required. This refinement process is called as Normalization. I know all of you are clear with the definition, let’s go with:
What is the need of normalisation?
Why are the problems we can face if we proceed without normalisation?
What are the advantages of normalization?
Asking question to oneself is the best way to get familiar with all the concepts.
Basics of Normalization resolved with Examples
This type of dependency is called functional dependency. In above example Marks is functionally dependent on Student#Course#.
Other Functional dependencies in above examples are:
Course# -> CourseName
Course#-> IName(Assuming one course is taught by one and only one instructor )
IName -> Room# (Assuming each instructor has his /her own and non-shared room)
Marks ->Grade
Formally we can define functional dependency as: In a given relation R, X and Y are attributes. Attribute Y is functional dependent on attribute X if each value of X determines exactly one value of Y. This is represented as :