NIELIT 2016 MAR Scientist B - Section C: 44

Question

For a database relation $R(a,b,c,d)$ where the domains of $a,b,c,d$ include only atomic values, only the following functional dependencies and those that can be inferred from them hold:

$a\to c\\b\to d$

the relation is in

• A. first normal form but not in second normal form.
• B. second normal form but not in third normal form.
• C. third normal form.
• D. none of these.

Comments

Original Source of this question: GATE 1997

https://gateoverflow.in/2265/gate-cse-1997-question-6-9 

Answer 1

The candidate key for the relation is:  $ab$ ,  because  $ab^{+}=abcd$

Since,  $a \rightarrow c$  and  $b \rightarrow d$ are partial dependencies which are not allowed in $2$NF, the relation is hence in $1$NF.

Option A is correct.

Answer 2

A) first normal form but not in second normal form,

( ab)+=abcd..so , ab is a candidate key, so, a→c and b→d both are partial dependencies...and in 2NF it is not Allowed...and in the question it is given that  domains of a,b,c,d include only atomic values...So it is in 1NF..

Answer 3

ANS: A

CANDIATE KEY OF THIS RELATION IS AB

 

a→c

b→d

BOTH CONTAIN PARTIAL INDEPENDENCIES , AND IN 2ND NORMAL FORM PARTIAL INDEPENDENCIES IS NOT ALLOWED.

SO GIVEN RELATION IS ONLY IN 1ST NORMAL FORM.