In the relational model, database schema has lossless join property if the join

Question

In the relational model, database schema has lossless join property if the join produces the same structure as the original relation ? no further decomposition is possible the intersection of the relations is empty the join produces the same tuples as the original relation If set S (A, B,C) is a candidate key for the relation R(A, B, C, D, E), then which of the following must be true ? (A, B,D) must also be a candidate key for R D A, B or A,C or B, C must also be a candidate key for R D A, B, C, D must also be a candidate key for R none of these All of thel following are reasons for leaving a schema in a lower normal form except Desire to keep related items together in the same relation Performance requirements Desire to preserve functional dependencies in the same relation Desire to reduce replication ?

Explanation / Answer

1)

first for looseless join  

Union of two relation must be Origin relation

and intersection must be not null

so

Answer is

A And D

2)

defination of candidate key is below

The minimal (minimum )set of attribute which can uniquely identify is known as candidate key.

here all of the option A,B C are false

Answer - > D) None of this

3)

benefits of normalization are below

Normalization is a process of organizing the data in database to avoid data redundancy, insertion anomaly, update anomaly & deletion anomaly.

so we can discard Option B AND Option D

so Answer is

A) AND C)

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