Đề thi trắc nghiệm cơ sở dữ liệu trường Cao Thắng - phần 7 doc

43. Table Q{A , B , C , D} and a set of functional dependencies
A → B, C
D → C
The closure of {A D } is:
a) A D
b) A D B C
c) B C
d) None of the above
44. Consider the relation student(sno, sname, cname, cno) where
(sno, cno) or (sname,
cname) are candidate keys. There are functional dependencies
within the keys.
Giáo Trình Cơ Sở Dữ Liệu Trang 105
Biên soạn : Phan Tấn Quốc- Trường Cao Đẳng Kỹ Thuật Cao Thắng
The highest normal form whose requirements this relation
satisfies is:
(a) 1NF
(b) 2NF
(c) 3NF
(d) BCNF
45. Let R be a relation with attributes (B,I,N,R,U,L) and let the
following functional
dependencies hold.
B → I
B → N
N R → U
N R → L

I → U
Given the above functional dependencies, which of the following
functional dependencies does
not hold:
a) N R → U L
b) B R → L
c) B → U
d) I→ N R
46. Suppose relation R(S,G,F,Y,N) has the following functional
dependencies:
S → G
G → F
G F → S
S → Y
N → S
Y → N
Which of the following is not a key?
a) N b) G,F
c) S d) Y
47. Table TT {A , N , H , K , J , O , X } and a set of functional
dependencies
A, N → O, X
Giáo Trình Cơ Sở Dữ Liệu Trang 106
Biên soạn : Phan Tấn Quốc- Trường Cao Đẳng Kỹ Thuật Cao Thắng
J → A , N, H
H, O → K, X
H, K, X → O
A, N, X → J
The closure of {A N } is:
e) A H K X J O

f) A N H K X J
g) A N H X J O
h) A N H K X J O
48. Consider the follow attributes and functional dependencies:
A B C D E F H
A→ D
AE → H
DF → BC
E → C
H → E
List all keys (not superkeys):
49. (Đề 48) Consider the decomposition into 3 relations: (AD) (EC)
(ABEFH). Is this
decomposition in
(a) BCNF
(b) 3NF
(c) 1NF
(d) None of the above