Lossless-Join Decomposition
Encyclopedia
Can also be called Nonadditive.
If you decompose a relation into relations and you will guarantee a Lossless-Join if ⋈ = .
Let be a relation schema.
Let be a set of functional dependencies
on .
Let and form a decomposition of .
The decomposition is a lossless-join decomposition of R if at least one of the following functional dependencies are in +(where + stands for the closure for every attribute in ):
If you decompose a relation into relations and you will guarantee a Lossless-Join if ⋈ = .
Let be a relation schema.
Let be a set of functional dependencies
Functional dependency
A functional dependency is a constraint between two sets of attributes in a relation from a database.Given a relation R, a set of attributes X in R is said to functionally determine another attribute Y, also in R, if, and only if, each X value is associated with precisely one Y value...
on .
Let and form a decomposition of .
The decomposition is a lossless-join decomposition of R if at least one of the following functional dependencies are in +(where + stands for the closure for every attribute in ):
- ∩ →
- ∩ →