Database-Management-System
August 29, 2024Database-Management-System
August 29, 2024Database-Management-System
| Question 809 |
Consider the following functional dependencies in a database:
A → B
B → C
D → E
E → D
F → G
F → H
(E,F) → I
The relation (E,D,A,B) is :
A → B
B → C
D → E
E → D
F → G
F → H
(E,F) → I
The relation (E,D,A,B) is :
| 2 NF | |
| 3 NF | |
| BCNF | |
| None of the above |
Question 809 Explanation:
Functional dependencies of the given subrelation R(E,D,A,B) are:
A → B
D → E
E → D
Since A is not determined by any of the given functional dependencies for R(E,D,A,B) so it must be included in the key now check whether “A” is the Primary key or not.
(A)+ = {A}
(AB)+ = {AB}
(AD)+ = {ABDE}
(AE)+ = {ABDE}
So (AD)+ and (AE)+ are the primary keys of R(E,D,A,B).
A → B, in this given FD there exist a partial dependency because here a prime key attribute(attribute which is a part of primary key but not a primary key itself of a function) which is determining a non-key attribute.
So the relation R(E,D,A,B) is not in 2NF .
A → B
D → E
E → D
Since A is not determined by any of the given functional dependencies for R(E,D,A,B) so it must be included in the key now check whether “A” is the Primary key or not.
(A)+ = {A}
(AB)+ = {AB}
(AD)+ = {ABDE}
(AE)+ = {ABDE}
So (AD)+ and (AE)+ are the primary keys of R(E,D,A,B).
A → B, in this given FD there exist a partial dependency because here a prime key attribute(attribute which is a part of primary key but not a primary key itself of a function) which is determining a non-key attribute.
So the relation R(E,D,A,B) is not in 2NF .
Correct Answer: D
Question 809 Explanation:
Functional dependencies of the given subrelation R(E,D,A,B) are:
A → B
D → E
E → D
Since A is not determined by any of the given functional dependencies for R(E,D,A,B) so it must be included in the key now check whether “A” is the Primary key or not.
(A)+ = {A}
(AB)+ = {AB}
(AD)+ = {ABDE}
(AE)+ = {ABDE}
So (AD)+ and (AE)+ are the primary keys of R(E,D,A,B).
A → B, in this given FD there exist a partial dependency because here a prime key attribute(attribute which is a part of primary key but not a primary key itself of a function) which is determining a non-key attribute.
So the relation R(E,D,A,B) is not in 2NF .
A → B
D → E
E → D
Since A is not determined by any of the given functional dependencies for R(E,D,A,B) so it must be included in the key now check whether “A” is the Primary key or not.
(A)+ = {A}
(AB)+ = {AB}
(AD)+ = {ABDE}
(AE)+ = {ABDE}
So (AD)+ and (AE)+ are the primary keys of R(E,D,A,B).
A → B, in this given FD there exist a partial dependency because here a prime key attribute(attribute which is a part of primary key but not a primary key itself of a function) which is determining a non-key attribute.
So the relation R(E,D,A,B) is not in 2NF .