A directory of Objective Type Questions covering all the Computer Science subjects. Here you can access and discuss Multiple choice questions and answers for various compitative exams and interviews.

41. Consider the FDs given in above question. The relation R is
a. in 1NF, but not in 2NF
b. in 2NF, but not in 3NF
c. in 3NF, but not in BCNF
d. in BCNF
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Answer: (a).in 1NF, but not in 2NF

42. Which of the following is TRUE?
a. Every relation in 3NF is also in BCNF
b. A relation R is in 3NF if every non-prime attribute of R is fully functionally dependent on every key of R
c. Every relation in BCNF is also in 3NF
d. No relation can be in both BCNF and 3NF
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Answer: (c).Every relation in BCNF is also in 3NF

43. Consider a relational table with a single record for each registered student with the following attributes.

1. Registration_Num: Unique registration number
of each registered student
2. UID: Unique identity number, unique at the
national level for each citizen
3. BankAccount_Num: Unique account number at
the bank. A student can have multiple accounts
or join accounts. This attribute stores the
primary account number.
4. Name: Name of the student
5. Hostel_Room: Room number of the hostel

Which one of the following option is INCORRECT?
a. BankAccount_Num is candidate key
b. Registration_Num can be a primary key
c. UID is candidate key if all students are from the same country
d. If S is a superkey such that S∩UID is NULL then S∪UID is also a superkey
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Answer: (a).BankAccount_Num is candidate key

44. Consider a relational table with a single record for each registered student with the following attributes.

1. Registration_Num: Unique registration number
of each registered student
2. UID: Unique identity number, unique at the
national level for each citizen
3. BankAccount_Num: Unique account number at
the bank. A student can have multiple accounts
or join accounts. This attribute stores the
primary account number.
4. Name: Name of the student
5. Hostel_Room: Room number of the hostel

Which one of the following option is INCORRECT?
a. BankAccount_Num is candidate key
b. Registration_Num can be a primary key
c. UID is candidate key if all students are from the same country
d. If S is a superkey such that S∩UID is NULL then S∪UID is also a superkey
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Answer: (a).BankAccount_Num is candidate key

45. Consider the following relational schema:

Suppliers(sid:integer, sname:string, city:string, street:string)
Parts(pid:integer, pname:string, color:string)
Catalog(sid:integer, pid:integer, cost:real)
(sid,pid are primary keys)
Assume that, in the suppliers relation above, each supplier and each street within a city has a unique name, and (sname, city) forms a candidate key. No other functional dependencies are implied other than those implied by primary and candidate keys. Which one of the following is TRUE about the above schema?
a. The schema is in BCNF
b. The schema is in 3NF but not in BCNF
c. The schema is in 2NF but not in 3NF
d. The schema is not in 2NF
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Answer: (a).The schema is in BCNF

46. Consider the following relational schemes for a library database: Book (Title, Author, Catalog_no, Publisher, Year, Price) Collection (Title, Author, Catalog_no) with in the following functional dependencies:

I. Title Author --> Catalog_no
II. Catalog_no --> Title, Author, Publisher, Year
III. Publisher Title Year --> Price

Assume {Author, Title} is the key for both schemes. Which of the following statements is true?
a. Both Book and Collection are in BCNF
b. Both Book and Collection are in 3NF only
c. Book is in 2NF and Collection is in 3NF
d. Both Book and Collection are in 2NF only
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Answer: (c).Book is in 2NF and Collection is in 3NF

47. Consider the relation scheme R = {E, F, G, H, I, J, K, L, M, M} and the set of functional dependencies {{E, F} -> {G}, {F} -> {I, J}, {E, H} -> {K, L}, K -> {M}, L -> {N} on R. What is the key for R?
a. {E, F}
b. {E, F, H}
c. {E, F, H, K, L}
d. {E}
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Answer: (b).{E, F, H}

48. Given the following two statements:

S1: Every table with two single-valued
attributes is in 1NF, 2NF, 3NF and BCNF.

S2: AB->C, D->E, E->C is a minimal cover for
the set of functional dependencies
AB->C, D->E, AB->E, E->C.

Which one of the following is CORRECT?
a. S1 is TRUE and S2 is FALSE
b. Both S1 and S2 are TRUE
c. S1 is FALSE and S2 is TRUE
d. Both S1 and S2 are FALSE
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Answer: (a).S1 is TRUE and S2 is FALSE

49. The maximum number of superkeys for the relation schema R(E,F,G,H) with E as the key is
a. 5
b. 6
c. 7
d. 8
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Answer: (d).8

50. Which one of the following statements about normal forms is FALSE?
a. BCNF is stricter than 3NF
b. Lossless, dependency-preserving decomposi­tion into 3NF is always possible
c. Lossless, dependency-preserving decomposi­tion into BCNF is always possible
d. Any relation with two attributes is in BCNF
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Answer: (c).Lossless, dependency-preserving decomposi­tion into BCNF is always possible

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