Database - The Relational Model and Normalization - Discussion
Discussion Forum : The Relational Model and Normalization - General Questions (Q.No. 19)
19.
If attribute A determines both attributes B and C, then it is also true that:
Discussion:
22 comments Page 1 of 3.
Kamlesh said:
1 decade ago
* Subset Property (Axiom of Reflexivity): If Y is a subset of X, then X → Y
* Augmentation (Axiom of Augmentation): If X → Y, then XZ → YZ
* Transitivity (Axiom of Transitivity): If X → Y and Y → Z, then X → Z
Hence the answer A->B is perfect, any option of A->B or A->c is right, but there is no A->c option is available, so A->B is the right answer.
* Augmentation (Axiom of Augmentation): If X → Y, then XZ → YZ
* Transitivity (Axiom of Transitivity): If X → Y and Y → Z, then X → Z
Hence the answer A->B is perfect, any option of A->B or A->c is right, but there is no A->c option is available, so A->B is the right answer.
Rohit bhatia said:
7 years ago
@ALL.
Every time attribute A appears, it is matched with the same value of attribute B, but not the same value of attribute C. Therefore, it is true that:
A. A -> B.
B. A -> C.
C. A -> (B,C).
D. (B,C) -> A.
Answer: Option A.
So, How it's answer is same as above question? Please, anyone explain me.
Every time attribute A appears, it is matched with the same value of attribute B, but not the same value of attribute C. Therefore, it is true that:
A. A -> B.
B. A -> C.
C. A -> (B,C).
D. (B,C) -> A.
Answer: Option A.
So, How it's answer is same as above question? Please, anyone explain me.
Priyanka said:
1 decade ago
I think that functional dependency do not say that if A->B then B->A is also true. For instance, if the roll_no of a student determines the name of that student then it is not true that the name of the student will recognize the roll_no of that particular student.
M,Ajay said:
1 decade ago
From hypothesis we can write A-> (BC) ,
According to the decomposition rule of functional dependency (FD) , we can write the above FD as A->B and A->C. So according to given options A->B is the correct answer.
According to the decomposition rule of functional dependency (FD) , we can write the above FD as A->B and A->C. So according to given options A->B is the correct answer.
Nitish said:
1 decade ago
The question is saying that A determines both B and C. But no option suggest that A is determining C.
Really have no idea what should be the correct answer?
Please suggest the correct answer with reason.
Really have no idea what should be the correct answer?
Please suggest the correct answer with reason.
Hemant said:
1 decade ago
In simple words it can be said that if from a bigger set of entries i.e. A we can take out B and similarly C, but it is not necessary we obtain A from both B and c. Vice versa not true.
Rupesh said:
10 years ago
Solution of this question is not right. According to your question an attribute A determines both B and C, then answer must be A->B, A->C or A->(B, C) or A->BC.
Jyothi said:
1 decade ago
Its true priyanka .
I think it might b different ans other than A->B, because its alreday mentioned na that A->B & A->C.Then how the ans can b again A->B
I think it might b different ans other than A->B, because its alreday mentioned na that A->B & A->C.Then how the ans can b again A->B
Pradeep said:
1 decade ago
Attribute A determines attributes B and C so,
A->BC, or A->B and A->C, in the three option only one option are given hence option a are right.
A->BC, or A->B and A->C, in the three option only one option are given hence option a are right.
Prachi said:
9 years ago
There is a different between determines and determine of.
If determine of then B->A but here determines B and C so A->B.
If determine of then B->A but here determines B and C so A->B.
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