Database - The Relational Model and Normalization - Discussion
Discussion Forum : The Relational Model and Normalization - General Questions (Q.No. 1)
1.
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:
Discussion:
23 comments Page 1 of 3.
Shahin said:
9 years ago
@Emil.
If A -> B holds then it's not necessary the B -> A also hold true.
A B
----------------------------
b 5
b 5
c 5
For every occurrence of b in A there is value 5 in B hence A -> B.
But for every Value of B which is 5 is not same value in A (b,c two values in A).
Hence If A -> B holds then it's not necessary that B -> A also holds true.
If A -> B holds then it's not necessary the B -> A also hold true.
A B
----------------------------
b 5
b 5
c 5
For every occurrence of b in A there is value 5 in B hence A -> B.
But for every Value of B which is 5 is not same value in A (b,c two values in A).
Hence If A -> B holds then it's not necessary that B -> A also holds true.
(2)
RAHUL KUMAR said:
1 decade ago
According to question A->B.
That means A would have all the contents such as that of B.
So instead of using tends to operation. Here have to use the UNION operation (A U B).
And guys please look forward for this.
That means A would have all the contents such as that of B.
So instead of using tends to operation. Here have to use the UNION operation (A U B).
And guys please look forward for this.
Vishnu said:
1 decade ago
The functional dependency A->B states that the set of values present in A are also in the B so that's why it matches the values in the case of A and B but not with C.
Kash said:
1 decade ago
It is a general thing to be noticed that if A will be related to both B & C, then how can the value not be same to C. So option A is correct. !
Richa Chaurasia said:
1 decade ago
Because of every attribute of A will also match with B but not C.
And then value of A $ B will depend to each other.
A->B.
And then value of A $ B will depend to each other.
A->B.
Rahul said:
1 decade ago
A -> B means that, each value of A determines exactly one value of B. And B is functionally dependent on A.
Padmasri said:
1 decade ago
Because A can uniquely identifies B each time.
As per the rule A->B means if A is true then B is true.
As per the rule A->B means if A is true then B is true.
Emil said:
10 years ago
Is A-->B is same as B-->A. A matches with B, so is it true that B matches with A?
Khalid seid said:
1 decade ago
Value of B depends on value of A. i.e A is the determinant but B is the dependent.
ShivaKavya said:
1 decade ago
Because A can uniquely identifies B each time.
So A->B. Option A.
So A->B. Option A.
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