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

Consider the relation studentsno, 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

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