### What is the lossless or Nonadditive join property of a decomposition?

## What is the lossless or Nonadditive join property of a decomposition?

This property ensures that no spurious tuples are generated when a NATURAL JOIN operation is applied to the relations in the decomposition.

## What are the conditions for lossless join decomposition?

To check for lossless join decomposition using FD set, following conditions must hold: Union of Attributes of R1 and R2 must be equal to attribute of R. Each attribute of R must be either in R1 or in R2. Intersection of Attributes of R1 and R2 must not be NULL.

## What is lossless join decomposition explain with an example?

July 2014) In database design, a lossless join decomposition is a decomposition of a relation into relations. such that a natural join of the two smaller relations yields back the original relation. This is central in removing redundancy safely from databases while preserving the original data.

## What is the dependency preservation property for a decomposition?

The dependency preservation decomposition is another property of decomposed relational database schema D in which each functional dependency X -> Y specified in F either appeared directly in one of the relation schemas Ri in the decomposed D or could be inferred from the dependencies that appear in some Ri.

## What is the most important reason to achieve the lossless join property?

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.

## Is a decomposition lossless?

Decomposition is lossless if it is feasible to reconstruct relation R from decomposed tables using Joins. This is the preferred choice. The information will not lose from the relation when decomposed. The join would result in the same original relation.

## What is the difference between lossy and lossless decomposition?

Example to check whether given Decomposition Lossless Join Decomposition. Let there be a relational schema R(A, B, C)….Difference Between Lossless and Lossy Join Decomposition :

Lossless | Lossy |
---|---|

The common attribute of the sub relations is a superkey of any one of the relation. | The common attribute of the sub relation is not a superkey of any of the sub relation. |

## How do you know if decomposition is dependency preserving?

Consider a relation R R —> F{…with some functional dependency(FD)….} R is decomposed or divided into R1 with FD { f1 } and R2 with { f2 }, then there can be three cases: f1 U f2 = F —–> Decomposition is dependency preserving.

## What is the importance of dependency preservation during decomposition?

Dependency Preserving It is an important constraint of the database. In the dependency preservation, at least one decomposed table must satisfy every dependency.

## How is lossless decomposition useful in database?

## Does BCNF guarantee lossless decomposition?

3NF ensures lossless decomposition while BCNF does not. (R1,R2) is a lossless-join decomposition of R with respect to a set of FDs F if for every instance r of R that satisfies F: πR1(r) ⋈ πR2(r) = r.

## What may be the consequences if a decomposition is not lossless?

If the relation has no proper decomposition, then it may lead to problems like loss of information. Decomposition is used to eliminate some of the problems of bad design like anomalies, inconsistencies, and redundancy.

## Can a relation be both lossless join and dependency preserving?

A relation R is decomposed into two or more only if the decomposition is both lossless join and dependency preserving. Learn more about Other Decompositions here on this page.

## Why is FD a-> BC Lossless Join Decomposition?

This is lossless join decomposition because Suppose a relation R (A,B,C,D) with FD set {A->BC} is decomposed into R1 (ABC) and R2 (AD) which is dependency preserving because FD A->BC is a part of R1 (ABC)

## What’s the difference between a lossy decomposition and a lossless decomposition?

The decompositions R1, R2, R2…Rn for a relation schema R are said to be Lossy if there natural join results into additon of extraneous tuples with the the original relation R. Formally, Let R be a relation and R1, R2, R3 … Rn be it’s decomposition, the decomposition is lossless if – Formally, Let R be a relation and R1, R2, R3 …

## When is decomposition done in a relational model?

Decomposition of a relation is done when a relation in relational model is not in appropriate normal form. Relation R is decomposed into two or more relations if decomposition is lossless join as well as dependency preserving.

What is the lossless or Nonadditive join property of a decomposition? This property ensures that no spurious tuples are generated when a NATURAL JOIN operation is applied to the relations in the decomposition. What are the conditions for lossless join decomposition? To check for lossless join decomposition using FD set, following conditions must hold: Union…