DBMS Multiple choice Questions and Answers-Relational Databases

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

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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.

Discuss

Answer: (b).Two relations are created.