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A relation is in 1NF if, and only if, it contains no repeating attributes or groups of attributes. To remove the repeating group, either flatten the table and extend the key, or decompose the relation-leading to First Normal Form. If the repeating group was flattened, as in the Student 2 data table, it will look something similar to:.
Even though this is an improvement, we still have an issue. So we need to find a new primary key — in such case it must be be a compound key since no single attribute can uniquely identify a row. With the relation in its flattened form, strange anomalies appear in the system.
Redundant data is the primary reason behind insertion, deletion, and updating anomalies. With the primary key including subject, we cannot enter a new student until they have at least one subject to study. This is called the insertion anomaly. If the name of a student were changed for example Smith, J.
This would be the same for any student who was studying only one subject and the subject was deleted. Again the problem arises from the necessity to have a compound primary key.
The alternative approach is to split the table into two parts, one for the repeating groups and one for the non-repeating groups. The primary key for the original relation is included in both of the new relations. A relation is in 2NF if, and only if, it is in 1NF and every non-key attribute is fully functionally dependent on the whole key.
Thus the relation is in 1NF with no repeating groups, and all non-key attributes must depend on the whole key, not just some part of it. A different way of saying this is that there must be no partial key dependencies PKDs.
To convert a relation with partial functional dependencies to 2NF, Create a set of new relations, i. Third Normal Form is an even stricter normal form and removes virtually all the redundant data. A relation is in 3NF if, and only if, it is in 2NF and there are no transitive functional dependencies. Transitive functional dependencies arise whenever one non-key attribute is functionally dependent on another non-key attribute.
To convert a relation with transitive functional dependencies to 3NF, eliminate the attributes involved in the transitive dependency and put them in a new relation.
DBMS (Database Management System) Normalization Study Material for IBPS IT Officer :
By definition transitive functional dependency can only occur in cases where there is more than one non-key field, so we can say that a relation in 2NF with Zero or one non-key field must automatically be in 3NF. This form deals with certain type of anamoly that is not handled by 3NF.
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DBMS MCQ - Multiple Choice Question and Answer
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(Part 1) MCQ On DBMS -- Database Management System
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