1. For the given database schema: R1(A,B,C,D) R2(A,E) R3(B,F,H) R4(C,G) R5(H,I)
ID: 3824425 • Letter: 1
Question
1. For the given database schema:
R1(A,B,C,D)
R2(A,E)
R3(B,F,H)
R4(C,G)
R5(H,I)
Please list all the foreign keys in R1.
a.
A
b.
B
c.
C
d.
All of A, B, and C are foreign key in R1
2. Given universal schema R(A,B,C,D,E,F,G,H,I) and a set of functional dependencies as follows:
AB CD
A E
B FH
C G
D B
G C
H I
when schema R(A,B,C,D,E,F,G,H,I) is normalized or decomposed into the following schema:
R1(A,B,C,D)
R2(A,E)
R3(B,F,H)
R4(C,G)
R5(H,I)
a.
The normalized schema:
R1(A,B,C,D)
R2(A,E)
R3(B,F,H)
R4(C,G)
R5(H,I)
possesses the lossless join decomposition property.
b.
The normalized schema:
R1(A,B,C,D)
R2(A,E)
R3(B,F,H)
R4(C,G)
R5(H,I)
possesses the functional dependency preservation property.
c.
Both a. and b.
d.
neither a. nor b.
a.
A
b.
B
c.
C
d.
All of A, B, and C are foreign key in R1
Explanation / Answer
1. d. All of A, B, and C are foreign key in R1
Attribute A in R1 is foreign key to R2, B is foreign key in R1 to R3 and attribute C is foreign key in R1 to R4
2. c. Both a. and b.
The normalized schema:
R1(A,B,C,D)
R2(A,E)
R3(B,F,H)
R4(C,G)
R5(H,I)
possesses the lossless join decomposition property as after joining the normalized relations we can get the original relation without any loss of data.
It also possesses the functional dependency preservation property as the functional dependencies in the original relation are preserved in the decomposed normalized relations.
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