In our previous lecture we discussed
Most of all basics of the Relational databases
Objectives of Normalization
Modification anomalies includes Deletion Anomaly and Insertion Anomaly also Updation Anomaly
Functional Dependencies and Fully Functional Dependencies with Armstrong’s axioms of FD etc.
Now we have to talk about Normalization and Different forms of normalization.
- Refinement of the database specifically ER model.
- Process of removing the anomalies of database/s and also
- Segregation of data over many entities or relations.
Need for Normalisation
- Improves database design.
- Ensures minimum redundancy of data.
- To make database structure flexible
- Reduces need to reorganize data when design is modified or enhanced.
- To achieve consistency as a result Removes modification anomalies. So, Normalized model converted to physical database tables.
Classes of Relation
Relation can be classified by the types of modification anomalies to which they are vulnerable.
The classes of relations and techniques for preventing anomalies are called normal forms.
Depending on its structure, a relation might be in first normal form, second normal form, and third normal form or some other normal form.
E.F. Codd defined first, second, and third normal forms (1NF, 2NF and 3NF). Later, Boyce-Codd normal form (BCNF) was postulated, and then fourth and fifth normal forms were designed.
Thus a relation that is in second form is also in first normal form. A relation in 5NF is also in 4NF, BCNF, 3NF, 2NF and 1NF.
First Normal Form (1NF)
Every relation is, by definition, in first normal form. That is because a relation, has no repeating groups in it – that is the characteristic of the first normal form.
In easy words, only one value is associated with each attribute and the value is not a set of values or a list of values.
Furthermore, Let us study with the help of example about this non repeating group characteristic
Anomalies in 1NF
The first normal form was related to the structure of the representation but the second normal form is related to eliminate data redundancy in these relations.
Before going to 2NF let us discuss the problems of 1NF. The problems can be listed as.
- Deletion anomaly
- Insertion anomaly
- Updation anomaly