Attention reader! The attributes in R will appear in at least one relation schema Ri in the decomposition, i. This is called the Attribute Preservation condition of decomposition. If a decomposition is not dependency preserving some dependency is lost in decomposition. To check this condition, take the JOIN of 2 or more relations in the decomposition. Each Functional Dependency specified in F either appears directly in one of the relations in the decomposition.
It is not necessary that all dependencies from the relation R appear in some relation Ri. It is sufficient that the union of the dependencies on all the relations Ri be equivalent to the dependencies on R. Skip to content.
It should always be lossless, because it confirms that the information in the original relation can be accurately reconstructed based on the decomposed relations.
If there is no proper decomposition of the relation, then it may lead to problems like loss of information. Properties of Decomposition Following are the properties of Decomposition, 1. Lossless Decomposition 2. Dependency Preservation 3. Lack of Data Redundancy 1. Lossless Decomposition Decomposition must be lossless. It means that the information should not get lost from the relation that is decomposed. It gives a guarantee that the join will result in the same relation as it was decomposed.
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