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What makes a table 3NF?
F. Codd’s definition states that a table is in 3NF if and only if both of the following conditions hold: The relation R (table) is in second normal form (2NF). Every non-prime attribute of R is non-transitively dependent on every key of R.
Why is third normal form important?
Third Normal Form (3NF) is considered adequate for normal relational database design because most of the 3NF tables are free of insertion, update, and deletion anomalies. Moreover, 3NF always ensures functional dependency preserving and lossless.
What is 3NF in sql?
Third Normal Form (3NF) 3NF is used to reduce the data duplication. It is also used to achieve the data integrity. If there is no transitive dependency for non-prime attributes, then the relation must be in third normal form.
What is a transitive functional dependency?
A functional dependency X → Y in a relation R is a transitive dependency if there is a set of attributes Z that is not a subset of any key of R, and both X → Z and Z → Y hold. In this case we must split this relation into two new relations and a join between both will recover the original relation.
What is the purpose of going to 3NF?
The purpose of going to 3NF is that on this normal form, we will eliminate functional dependencies on non-key fields. At this stage, all non-key fields are dependent only on the key.
When to use third normal form ( 3NF )?
X is a super key. Y is a prime attribute (each element of Y is part of some candidate key). A relation that is in First and Second Normal Form and in which no non-primary-key attribute is transitively dependent on the primary key, then it is in Third Normal Form (3NF). Note – If A->B and B->C are two FDs then A->C is called transitive dependency.
When is a relation in a 3NF form?
A relation is in 3NF if at least one of the following condition holds in every non-trivial function dependency X –> Y: X is a super key. Y is a prime attribute (each element of Y is part of some candidate key).
What causes an update in third normal form?
This update anomaly is caused by a transitive dependency. We need to remove such dependencies by progressing to Third Normal Form (3NF). Third Normal Form (3NF): A relation is in third normal form, if there is no transitive dependency for non-prime attributes as well as it is in second normal form.