What is Normalization
Normalization is the procedure to split the relation into relations with less attributes thereby minimizing the redundancy of the data and minimizing the insertions, deletions and updating. In other words we can say that the normalization is that process in which we renovate an un-normalized relation into relations. There is a sequence of stages or steps on which the normalization works. This sequence is called normal forms. The normal forms are relevant to entity relations. If the form satisfies a certain sets of constraints then a table or a relation comes to the particular normal form. There are above five normal forms. These are 1NF, 2NF, 3NF, 4NF and 5NF. Here NF stands Normal Form. It is very important for relational data model to consider that the first normal form (1NF) is very grave in creating the relations. Rests of all the forms are optional. There are some guidelines which help to create a good database. There is always a need for updating the database, so that there are three anomalies for data modification.
Advantages and Disadvantages of normalization
Advantages of normalization are as follows-
With these advantages there are some disadvantages of normalization given below-
Types of Normalization
There is a series of normal forms but the most commonly used normal forms are 1NF, 2NF and 3NF given below.
Can we use functions in where clause? Why do we use "AS" in alias name? Can we use alias name in "group by" Clause and "order by" clause?
The theory given for the normalization is good.But I would like to give a feedback that the explanation given to the normal forms is too confusing. Some normal forms don't have an example. It could be made more understandable by including functional dependencies. This is the way we could get a better idea.
I would like to correct the explanation given for 1NF- This normal form requires atomicity. Example: If I have a relation.
To make this relation in 1NF it would look as follows
This is done in order to overcome anomalies that occur in databases.
2NF - this mainly lays focus that there should not be partial dependency.
eg ab is candidate key
c,d,e,f are non prime attributes
so there can never be a situation where subset of candidate is functional dependent on non prime attribute
a->d (not in 2 NF)
3 NF- This normal forms basically tells that there should not be transitive dependency that is
a->b and b->c
then a->c (transitive dependency).This should not exist.