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. The relational model consists of:
a. data in the form of tables.
b. data redundancy.
c. operations using non-SQL languages.
d. unorganized data.
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Answer: (a).data in the form of tables.

42. A primary key is which of the following?
a. Any attribute
b. An attribute that uniquely identifies each row
c. An attribute that uniquely identifies each column
d. A derived attribute
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Answer: (b).An attribute that uniquely identifies each row

43. A foreign key is which of the following?
a. Any attribute
b. The same thing as a primary key
c. An attribute that serves as the primary key of another relation
d. None of the above.
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Answer: (c).An attribute that serves as the primary key of another relation

44. Relations are:
a. two-dimensional tables.
b. three-dimensional tables.
c. four-dimensional tables.
d. five-dimensional tables.
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Answer: (a).two-dimensional tables.

45. A relation has which of the following properties?
a. Each row is not unique.
b. Attributes can have the same name within a given table.
c. Each relation has a unique name.
d. The order of the columns is significant.
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Answer: (c).Each relation has a unique name.

46. The entity integrity rule states that:
a. no primary key attribute may be null.
b. no primary key can be composite.
c. no primary key may be unique.
d. no primary key may be equal to a value in a foreign key.
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Answer: (a).no primary key attribute may be null.

47. When mapping a multivalued attribute into a relation which of the following is true?
a. One relation is created.
b. Two relations are created.
c. Three relations are created.
d. Four relations are created.
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Answer: (b).Two relations are created.

48. When mapping a regular entity into a relation which of the following is true?
a. One relation is created.
b. Two relations are created.
c. Three relations are created.
d. Four relations are created.
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Answer: (a).One relation is created.

49. When mapping a binary many-to-many relationship into a relation which of the following is true?
a. One relation is created.
b. Two relations are created.
c. Three relations are created.
d. Four relations are created.
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Answer: (c).Three relations are created.

50. When mapping a many-to-many unary relationship into a relation which of the following is true?
a. One relation is created.
b. Two relations are created.
c. Three relations are created.
d. Four relations are created.
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Answer: (b).Two relations are created.

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