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 following relational schemas for a library database: 
Book (Title, Author, Catalog_no, Publisher, Year, Price) 
Collection (Title, Author, with the following 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 schemas. Which one of the following is true ?
a. Both Book and Collection are in BCNF
b. Both Book and Collection are in 3NF
c. Book is in 2NF and Collection in 3NF
d. Both Book and Collection are in 2NF
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Answer: (c).Book is in 2NF and Collection in 3NF

42. Specialization Lattice stands for
a. An entity type can participate as a subclass in only one specialization
b. An entity type can participate as a subclass in more than one specialization
c. An entity type that can participate in one specialization
d. An entity type that can participate in one generalization
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Answer: (b).An entity type can participate as a subclass in more than one specialization

43.
Match the following with respect to the jump statements

List-I List-II

a. Timeout ordering protocol i. Wait for graph

b. Deadlock prevention ii. Roll back

c. Deadlock detection iii. Wait-die scheme

d. Deadlock recovery iv. Thomas Write Rule

Codes:
a b c d
a. iv       iii       i       ii
b. iii       ii       iv       i
c. ii       i       iv       iii
d. iii       i       iv       ii
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Answer: (a).iv       iii       i       ii

44. Consider the schema

R = {S,T, U,V}

and the dependencies

S →T, T → U, U → V and V → S

If   R   =   (R1  and   R2)   be   a decomposition such that R1 ∩ R2 = Ф

then the decomposition is
a. not in 2NF
b. in 2NF but not in 3NF
c. in 3NF but not in 2NF
d. in both 2NF and 3NF
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Answer: (d).in both 2NF and 3NF

45. Which of the following concurrency protocol ensures both conflict serializability deadlock:
I. 2-phase locking 
II. Time phase ordering 
a. Both I & II
b. II only
c. I only
d. Neither I nor II
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Answer: (b).II only

46. The "part-whole", or "a-part-of", relationship in which objects representing the components of something associated with an object representing the entire assembly is called as
a. Association
b. Aggregation
c. Encapsulation
d. Generalisation
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Answer: (b).Aggregation

47. If h is chosen from a universal collection of hash functions and is used to hash n keys into a table of size m, where n ≤ m, the expected number of collisions involving a particular key K is
a. less than 1
b. less than /g n
c. greater than 1
d. greater than /g n
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Answer: (a).less than 1

48. In RDBMS, the constraint that no key attribute (column) may be NULL is referred to as:
a. Referential integrity
b. Multi-valued dependency
c. Entity Integrity
d. Functional dependency
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Answer: (c).Entity Integrity

49. Which of the following statement(s) is/are FALSE in the context of Relational DBMS ? I. Views in a database system are important because they help with access control by allowing users to see only a particular subset of the data in the database. II. E-R diagrams are useful to logically model concepts. III. An update anomaly is when it is not possible to store information unless some other, unrelated information is stored as well. IV. SQL is a procedural language.
a. I and IV only
b. III and IV only
c. I, II and III only
d. II, III and IV only
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Answer: (b).III and IV only

50. In a relational database model, NULL values can be used for all but which one of the following?
a. To allow duplicate tuples in the table by filling the primary key column(s) with NULL
b. To avoid confusion with actual legitimate data values like 0 (zero) or integer columns and " (the empty string) for string columns
c. To leave columns in a tuple marked as "unknown" when the actual value is unknown
d. To fill a column in a tuple when that column does not really "exist" for that particular tuple
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Answer: (a).To allow duplicate tuples in the table by filling the primary key column(s) with NULL

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