Database Reference
In-Depth Information
5.5.6 Fifth Normal Form
5th Normal Form (5NF) removes cyclic dependencies. 5NF is also known as
Projection Normal Form (PJNF). 5NF is an case of
join dependencies
. A join dependency
shows the cyclical constraint “if Entity A is connected to Entity B, and Entity B is connec-
ted
to Entity C, and Entity C is aconnected back to Entity A, then all three entities must
necessarily coexist in the same tuple.” In other words , a fourth normal form table is in
fifth normal form if it cannot be non-loss decomposed into a series of smaller tables.
The last stage of normalization is Fifth Normal Form (5NF). 5NF normalization is achieved
when:
1. A table must be in 4NF.
2. A table is in 5NF if it cannot be made into any smaller tables with different keys
