Database Management Systems
Questions 311 to 320
A super key is any key that uniquely identifies each
(a) Entity uniquely (b) Object in a table (c) Table
(d) Structure in a table (e) Column uniquely.
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A table can be logically connected to another table by
defining a
(a) Hyperlink (b)
Common attribute (c)
Primary key
(d) Candidate key (e) Super Key.
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A primary key that consists of more than one field is
called a
(a) Composite key (b) Secondary key (c) Group key
(d) All of the above (e)
None of the above.
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Which of the following statements concerning the primary
key is true?
(a) All primary key entries are unique
(b) The primary key may be null
(c) The primary key is not required for all
tables
(d) The primary key data does not have to be
unique
(e) For every primary key there must be a
foreign key.
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In the context of a database table, the statement "A
determines B" indicates that
(a) Knowing the value of attribute A you can
not look up the value of attribute B
(b) You do not need to know the value of
attribute A in order to look up the value of attribute
(c) Knowing the value of attribute B you can
look up the value of attribute A
(d) Knowing the value of attribute A you can
look up the value of attribute B
(e) None of the above.
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A super key that does not contain a subset of attributes
that is itself a super key is called a
(a) Candidate key (b) Primary key (c)
Super key
(d) Secondary key (e) Foreign key.
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A table that displays data redundancies yields
____________ anomalies.
(a) Update (b)
Insertion (c)
Deletion
(d) All of the above (e) None of the above.
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A table is in the Fourth Normal Form (4NF) if
(a) All attributes must be dependent on the
primary key, and must be dependent on each other
(b) All attributes must be dependent on the
primary key, but must be independent of each other
(c) No row can contain two or more multivalued
facts about an entity
(d) A and C
(e) B and C.
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A table where all attributes are dependent on the primary
key and are independent of each other, and no row contains two or more
multivalued facts about an entity, is said to be in
(a) 1NF (b)
2NF (c) 3NF (d) 4NF (e) BCNF.
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The basic SQL aggregate function that gives the number of
rows containing not null values for the given column is
(a) MIN (b)
COUNT (c) MAX (d) SUM (e) AVG.
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Answers
Answer : (a)
Reason : Super key is
any key that uniquely identifies each entity uniquely
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Answer : (b)
Reason : Common
attribute is maintained to connect two tables logically
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Answer : (a)
Reason : A
primary key that consists of more than one field is called Composite key
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Answer : (a)
Reason: All primary
keys are unique.
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Answer : (d)
Reason : The answer
is evident
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Answer : (a)
Reason: The minimal
set of super key is called candidate key.
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Answer : (d)
Reason : Table
that displays data redundancies yields update, insertion, deletion anomalies
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Answer : (e)
Reason : The
answer is evident
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Answer : (d)
Reason : Answer
is obvious
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Answer : (b)
Reason : Count
function gives the number of rows containing not null values for the given
column
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312 - Correct answer is Primary Key
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