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+22 votes

A *prime attribute* of a relation scheme $R$ is an attribute that appears

- in all candidate keys of $R$
- in some candidate key of $R$
- in a foreign key of $R$
- only in the primary key of $R$

+29 votes

Best answer

0

@Sankar: yes you are correct it is sufficient if the prime attribute is in any of candidate key. did not read all the options , my bad

+44

Consider a relation $R(ABCDE)$ and $FD =\left \{ AB\rightarrow CD,C\rightarrow B,D\rightarrow E \right \}$.

Here Candidate key are $AB$ and $AC$.

Prime Attribute:$A$,$B$,$C$.

Now check is B is appearing in both C.K.?No

So prime attribute appears in some CK.

0

@ManojK sir , It wiould be nice if you could explain* ( or *verify ) *how to find the prime attribute*

*AFAIK* , Prime attributes are part of CK

Here CK are AB, AC . Dependncies invloving them

AB→CD

AC→B

AC→A [ Trivial ]

$\Rightarrow$ (Prime attributes are part of Key ) Prime attributes are **CD, C,D,B,A**

+6 votes

Answer (B).

The constituent attributes of a Candidate key or simply the attributes of a candidate key are called the prime attributes. Suppose ABC is one candidate key of a Relation R(ABCDEFGH). Then the attributes A, B and C all are prime attributes. Similarly if ABD is also another candidate key in the same relation R, then D is also the prime attribute. And conversely, an attribute that does not occur in ANY candidate key is called a non-prime attribute.

The constituent attributes of a Candidate key or simply the attributes of a candidate key are called the prime attributes. Suppose ABC is one candidate key of a Relation R(ABCDEFGH). Then the attributes A, B and C all are prime attributes. Similarly if ABD is also another candidate key in the same relation R, then D is also the prime attribute. And conversely, an attribute that does not occur in ANY candidate key is called a non-prime attribute.

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