The Relational Model and Normalization Questions and Answers

Q: For some relations, changing the data can have undesirable consequences called:

Correct answer: modification anomalies.A poorly structured relation makes some changes impossible to perform cleanly: an insertion anomaly prevents a fact being recorded until some unrelated fact is known, a deletion anomaly destroys information as a side effect, and an update anomaly requires the same value to be changed in many places. Normalisation exists to remove them.

Q: A key:

Correct answer: identifies a row.A key identifies rows, not columns, and it may consist of one attribute or several - a key of two or more is a composite key, but there is no requirement either way. What matters is that the combination be unique across the relation and minimal, so that no attribute could be dropped and uniqueness still hold.

Q: An attribute is a(n):

Correct answer: column of a table.An attribute is a column, corresponding to a field in file-processing terms, and it draws its values from a single domain. A row is a tuple, and the whole two-dimensional structure is the relation. A key is a role that one or more attributes play rather than a structural element in its own right.

Q: A relation in this form is free of all modification anomalies.

Correct answer: Domain/key normal formFagin proved that a relation in domain/key normal form has no modification anomalies of any kind, and conversely that any relation free of them is in DK/NF. It is defined by requiring that every constraint on the relation follow from its domain and key definitions alone. The difficulty is that there is no general procedure for putting a relation into it.

Q: If attributes A and B determine attribute C, then it is also true that:

Correct answer: (A,B) is a composite determinant.When two attributes together determine a third, the pair forms a composite determinant, and the dependency is on the pair as a whole. It does not follow that either attribute determines C on its own - if it did, the other would be redundant and the determinant would not be minimal. Nor does the dependency work in reverse.

Q: A tuple is a(n):

Correct answer: row of a table.A tuple is a row, the record of the older vocabulary. Since no two rows in a relation may be identical and the order of rows carries no meaning, a relation is formally a set of tuples - which is why a query result has no inherent ordering unless one is requested explicitly.

Q: If attribute A determines both attributes B and C, then it is also true that:

Correct answer: A → B.If A determines the pair (B, C), then it determines each of them separately: given a value of A, the value of B is fixed and so is the value of C. This is the decomposition rule of Armstrong’s axioms. The converse does not hold, so nothing follows in the reverse direction, and the other three options all reverse the arrow.

Q: In a relation, the order of the rows matters.

Correct answer: FalseRow order carries no meaning in a relation: a relation is a set of tuples, and a set has no inherent sequence. A query that needs its output in a particular order must request it explicitly, and any apparent ordering in a result set without such a request is an accident of storage and must not be relied on.

Q: In a relation, the rows are sometimes called "records."

Correct answer: TrueThe vocabularies correspond directly: relation, tuple and attribute in the formal relational terminology are table, record and field in the older file-processing one. The terms are used interchangeably in practice, and being fluent in both matters because textbooks and product documentation mix them freely.

61.

For some relations, changing the data can have undesirable consequences called:

A.referential integrity constraints.
B.modification anomalies.
C.normal forms.
D.transitive dependencies.

Answer: B

Correct answer: modification anomalies.

A poorly structured relation makes some changes impossible to perform cleanly: an insertion anomaly prevents a fact being recorded until some unrelated fact is known, a deletion anomaly destroys information as a side effect, and an update anomaly requires the same value to be changed in many places. Normalisation exists to remove them.

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62.

A key:

A.must always be composed of two or more columns.
B.can only be one column.
C.identifies a row.
D.identifies a column.

Answer: C

Correct answer: identifies a row.

A key identifies rows, not columns, and it may consist of one attribute or several - a key of two or more is a composite key, but there is no requirement either way. What matters is that the combination be unique across the relation and minimal, so that no attribute could be dropped and uniqueness still hold.

Discuss in Forum

63.

An attribute is a(n):

A.column of a table.
B.two dimensional table.
C.row of a table.
D.key of a table.

Answer: A

Correct answer: column of a table.

An attribute is a column, corresponding to a field in file-processing terms, and it draws its values from a single domain. A row is a tuple, and the whole two-dimensional structure is the relation. A key is a role that one or more attributes play rather than a structural element in its own right.

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64.

A relation in this form is free of all modification anomalies.

A.First normal form
B.Second normal form
C.Third normal form
D.Domain/key normal form

Answer: D

Correct answer: Domain/key normal form

Fagin proved that a relation in domain/key normal form has no modification anomalies of any kind, and conversely that any relation free of them is in DK/NF. It is defined by requiring that every constraint on the relation follow from its domain and key definitions alone. The difficulty is that there is no general procedure for putting a relation into it.

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65.

If attributes A and B determine attribute C, then it is also true that:

A.A → C.
B.B → C.
C.(A,B) is a composite determinant.
D.C is a determinant.

Answer: C

Correct answer: (A,B) is a composite determinant.

When two attributes together determine a third, the pair forms a composite determinant, and the dependency is on the pair as a whole. It does not follow that either attribute determines C on its own - if it did, the other would be redundant and the determinant would not be minimal. Nor does the dependency work in reverse.

Discuss in Forum

66.

A tuple is a(n):

A.column of a table.
B.two dimensional table.
C.row of a table.
D.key of a table.

Answer: C

Correct answer: row of a table.

A tuple is a row, the record of the older vocabulary. Since no two rows in a relation may be identical and the order of rows carries no meaning, a relation is formally a set of tuples - which is why a query result has no inherent ordering unless one is requested explicitly.

Discuss in Forum

67.

If attribute A determines both attributes B and C, then it is also true that:

A.A → B.
B.B → A.
C.C → A.
D.(B,C) → A.

Answer: A

Correct answer: A → B.

If A determines the pair (B, C), then it determines each of them separately: given a value of A, the value of B is fixed and so is the value of C. This is the decomposition rule of Armstrong’s axioms. The converse does not hold, so nothing follows in the reverse direction, and the other three options all reverse the arrow.

Discuss in Forum

68.

One solution to the multivalued dependency constraint problem is to:

A.split the relation into two relations, each with a single theme.
B.change the theme.
C.create a new theme.
D.add a composite key.

Answer: A

Correct answer: split the relation into two relations, each with a single theme.

A multivalued dependency problem arises when one relation holds two independent multivalued facts about the same key, forcing every combination of the two to be stored. Separating them into two relations, each carrying a single theme, removes the spurious combinations entirely - and this is exactly what putting the relation into fourth normal form means.

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69.

In a relation, the order of the rows matters.

A.True
B.False

Answer: B

Correct answer: False

Row order carries no meaning in a relation: a relation is a set of tuples, and a set has no inherent sequence. A query that needs its output in a particular order must request it explicitly, and any apparent ordering in a result set without such a request is an accident of storage and must not be relied on.

Discuss in Forum

70.

In a relation, the rows are sometimes called "records."

A.True
B.False

Answer: A

Correct answer: True

The vocabularies correspond directly: relation, tuple and attribute in the formal relational terminology are table, record and field in the older file-processing one. The terms are used interchangeably in practice, and being fluent in both matters because textbooks and product documentation mix them freely.

Discuss in Forum

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