Fifth Normal Form (5NF) is a state where a relation is decomposed into independent subrelations such that joining them back together does not lose or create any new data. To be in 5NF, a relation must be in 4NF and cannot be further decomposed without violating lossless join or introducing redundancy. A join dependency exists when a relation can be recreated by joining its decomposed subrelations based on their candidate keys. Being free of join dependencies means a relation is in 5NF.

1. Normalization
- Fifth Normal Form
- Ms.S.Athilakshmi
Asst.Prof, Department of Computer Science
Motto:Expertise and Excellence

2. Fifth Normal Form (5NF)
A relation R is in 5NF if and only if every non-trivial join dependency in R is implied
by the candidate keys of R.
A relation break up into two relations must contain lossless join Property, which
makes certain that no invalid or extra tuples of attributes are created when
relations are again joined together through a natural join.
Motto:Expertise and Excellence

3. Fifth Normal Form (5NF)
A database is said to be in 5NF, if and only if,
– It’s in 4NF
– If we can decompose table further to eliminate redundancy and anomaly, and
when we re-join the decomposed tables by means of candidate keys, we should
not be losing the original data or any new record set should not arise. In simple
words, joining two or more decomposed table should not lose records nor
create new records.
– 5NF is satisfied when all the tables are broken into as many tables as possible in
order to avoid redundancy.
– 5NF is also known as Project-join normal form (PJ/NF).
Motto:Expertise and Excellence

4. Join dependency
– A table or relation can be recreated or re-designed by joining multiple tables
and each table of this contain a subset of the attributes and values of the
table, then the table is in Join Dependency. It is a generalization of Multivalued
Dependency.
– If the join of R1 and R2 over S is equal to relation R then we can say that a join
dependency exists, where R1 and R2 are the decomposition R1 (P, Q, S) and R2
(Q, T) of a given relation R (P, Q, S, T). As a possibility, R1 and R2 are a lossless
decomposition of R.
Motto:Expertise and Excellence

5. Join dependency
– Join Dependency can be associated to 5NF, wherein a relation is in 5NF, only if it is
already in 4NF and it cannot be decomposed further.
Motto:Expertise and Excellence

6. Motto:Expertise and Excellence