Database Design Using Normalization Questions and Answers

Q: One common design problem when designing a database from existing data is the presence of missing values, called blank values, in received data.

Correct answer: FalseThe statement is right about the problem and wrong about its name. Missing values are called null values, not blank values, and the distinction matters because a null is not an empty string - it is the absence of a value, and it may mean unknown, not applicable, or simply not yet entered.

Q: Normalization requires programmers to write more complex SQL.

Correct answer: TrueNormalization distributes data across more tables, so retrieving what was once a single row now requires joins, and more complex conditions and subqueries besides. This is one of the two standard disadvantages set against the elimination of modification anomalies, and it is the reason denormalization is sometimes chosen for read-only data.

Q: One common design problem when designing a database from existing data is the presence of inconsistent values in the received data.

Correct answer: TrueInconsistent values - the same thing recorded in different ways, with variant spellings, word orders or punctuation - are among the commonest problems in received data. They break grouping, counting and joining, and the standard way of exposing them is a GROUP BY on the column, which puts each variant in its own group.

Q: When building a database from an existing set of tables, we may safely assume that there are no multivalued dependencies in the data we are given.

Correct answer: FalseNothing about received data guarantees the absence of multivalued dependencies; the tables were designed by someone else, possibly with no normalization at all. Their presence must be established by examining the data and understanding what it means, and where one is found the relation should be split so that each holds a single theme.

Q: Surrogate keys have much meaning for users.

Correct answer: FalseA surrogate key is an artificial identifier - typically a system-generated integer - with no relationship to the data it identifies, which is exactly the point: it never changes, it is short, and it is guaranteed unique. The cost is that it means nothing to a user, so a meaningful candidate key usually has to be kept alongside it and given a unique constraint.

51.

One common design problem when designing a database from existing data is the presence of missing values, called blank values, in received data.

A.True
B.False

Answer: B

Correct answer: False

The statement is right about the problem and wrong about its name. Missing values are called null values, not blank values, and the distinction matters because a null is not an empty string - it is the absence of a value, and it may mean unknown, not applicable, or simply not yet entered.

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52.

Normalization requires programmers to write more complex SQL.

A.True
B.False

Answer: A

Correct answer: True

Normalization distributes data across more tables, so retrieving what was once a single row now requires joins, and more complex conditions and subqueries besides. This is one of the two standard disadvantages set against the elimination of modification anomalies, and it is the reason denormalization is sometimes chosen for read-only data.

Discuss in Forum

53.

One common design problem when designing a database from existing data is the presence of inconsistent values in the received data.

A.True
B.False

Answer: A

Correct answer: True

Inconsistent values - the same thing recorded in different ways, with variant spellings, word orders or punctuation - are among the commonest problems in received data. They break grouping, counting and joining, and the standard way of exposing them is a GROUP BY on the column, which puts each variant in its own group.

Discuss in Forum

54.

When building a database from an existing set of tables, we may safely assume that there are no multivalued dependencies in the data we are given.

A.True
B.False

Answer: B

Correct answer: False

Nothing about received data guarantees the absence of multivalued dependencies; the tables were designed by someone else, possibly with no normalization at all. Their presence must be established by examining the data and understanding what it means, and where one is found the relation should be split so that each holds a single theme.

Discuss in Forum

55.

Surrogate keys have much meaning for users.

A.True
B.False

Answer: B

Correct answer: False

A surrogate key is an artificial identifier - typically a system-generated integer - with no relationship to the data it identifies, which is exactly the point: it never changes, it is short, and it is guaranteed unique. The cost is that it means nothing to a user, so a meaningful candidate key usually has to be kept alongside it and given a unique constraint.

Discuss in Forum

Database Design Using Normalization Questions and Answers

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Database Design Using Normalization Questions and Answers

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