Database Design Using Normalization Questions and Answers

Q: Proper normalization eliminates duplicated data.

Correct answer: TrueA normalized design stores each fact in one place, which is what makes update anomalies impossible: there is no second copy to fall out of step. Foreign key values are repeated, but they are the mechanism by which relations are linked rather than duplicated data, and they are maintained by referential integrity rather than by hand.

Q: For a number of reasons, normalizations is not often an advantage for a(n) ________ database.

Correct answer: read-onlyNormalization exists to prevent modification anomalies, and a database that is never updated cannot suffer them. What remains is the cost: more tables, more joins, more complex and slower queries. So for a read-only database the balance tips the other way, and deliberately denormalized structures are the norm - which is exactly what a data warehouse star schema is.

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: When you are given a set of tables and asked to create a database to store their data, the first step is to create the new database.

Correct answer: FalseCreating the database comes last. The first step is to examine what you have been given - count the rows, look at the columns and the data in them - then work out the dependencies and keys, then test the referential integrity constraints. Building the new database before understanding the old data means building the old problems into it.

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.

Q: When assessing the table structure of an acquired set of tables with data, determining foreign keys is (part of) the:

Correct answer: second step.Determining functional dependencies, primary keys and foreign keys all belong to the second step, in which the structure implied by the data is worked out. The first step is simply to see what is there - the row count and the columns - and the third is to test whether the referential integrity constraints implied by the foreign keys actually hold.

Q: We use the SQL construct COUNT(*) to count the number of rows in a table.

Correct answer: TrueCOUNT(*) counts the rows in a table or in each group of a grouped query, including rows containing nulls. It is the first thing to run on an acquired table, since the row count establishes the scale of what you are dealing with before any structural inference is attempted.

Q: The design guidelines and priorities for read-only databases are different because read-only databases are never updated.

Correct answer: TrueBecause a read-only database is never updated, modification anomalies cannot occur, and the chief reason for normalizing disappears. What remains is the cost of joins, so the priorities invert: denormalized structures that answer queries in fewer joins are preferred, and the design is judged on retrieval performance rather than on update integrity.

Q: When assessing the table structure of an acquired set of tables with data, accessing the validity of possible referential integrity constraints on foreign keys is (part of) the:

Correct answer: third step.The assessment proceeds in order: first count the rows and examine the columns to see what is there, then determine the functional dependencies, primary keys and foreign keys, then assess whether the referential integrity constraints those foreign keys imply are actually satisfied by the data. The check comes third because it cannot be made until the foreign keys have been identified.

Q: Most of the time, modification anomalies are serious enough that tables should be normalized into:

Correct answer: BCNF.Boyce-Codd Normal Form requires every determinant to be a candidate key, and a table satisfying it is free of the anomalies that arise from functional dependencies. Third normal form leaves some cases unhandled, which is why BCNF rather than 3NF is the practical target. Beyond it, 4NF deals with multivalued dependencies, which are a separate matter.

11.

Proper normalization eliminates duplicated data.

A.True
B.False

Answer: B

Correct answer: True

A normalized design stores each fact in one place, which is what makes update anomalies impossible: there is no second copy to fall out of step. Foreign key values are repeated, but they are the mechanism by which relations are linked rather than duplicated data, and they are maintained by referential integrity rather than by hand.

Discuss in Forum

12.

For a number of reasons, normalizations is not often an advantage for a(n) ________ database.

A.read-only
B.updateable
C.either a read-only or an updateable
D.None of the above is correct.

Answer: A

Correct answer: read-only

Normalization exists to prevent modification anomalies, and a database that is never updated cannot suffer them. What remains is the cost: more tables, more joins, more complex and slower queries. So for a read-only database the balance tips the other way, and deliberately denormalized structures are the norm - which is exactly what a data warehouse star schema is.

Discuss in Forum

13.

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

14.

When you are given a set of tables and asked to create a database to store their data, the first step is to create the new database.

A.True
B.False

Answer: B

Correct answer: False

Creating the database comes last. The first step is to examine what you have been given - count the rows, look at the columns and the data in them - then work out the dependencies and keys, then test the referential integrity constraints. Building the new database before understanding the old data means building the old problems into it.

Discuss in Forum

15.

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

16.

When assessing the table structure of an acquired set of tables with data, determining foreign keys is (part of) the:

A.first step.
B.second step.
C.third step.
D.fourth step.

Answer: B

Correct answer: second step.

Determining functional dependencies, primary keys and foreign keys all belong to the second step, in which the structure implied by the data is worked out. The first step is simply to see what is there - the row count and the columns - and the third is to test whether the referential integrity constraints implied by the foreign keys actually hold.

Discuss in Forum

17.

We use the SQL construct COUNT(*) to count the number of rows in a table.

A.True
B.False

Answer: A

Correct answer: True

COUNT(*) counts the rows in a table or in each group of a grouped query, including rows containing nulls. It is the first thing to run on an acquired table, since the row count establishes the scale of what you are dealing with before any structural inference is attempted.

Discuss in Forum

18.

The design guidelines and priorities for read-only databases are different because read-only databases are never updated.

A.True
B.False

Answer: A

Correct answer: True

Because a read-only database is never updated, modification anomalies cannot occur, and the chief reason for normalizing disappears. What remains is the cost of joins, so the priorities invert: denormalized structures that answer queries in fewer joins are preferred, and the design is judged on retrieval performance rather than on update integrity.

Discuss in Forum

19.

When assessing the table structure of an acquired set of tables with data, accessing the validity of possible referential integrity constraints on foreign keys is (part of) the:

A.first step.
B.second step.
C.third step.
D.fourth step.

Answer: C

Correct answer: third step.

The assessment proceeds in order: first count the rows and examine the columns to see what is there, then determine the functional dependencies, primary keys and foreign keys, then assess whether the referential integrity constraints those foreign keys imply are actually satisfied by the data. The check comes third because it cannot be made until the foreign keys have been identified.

Discuss in Forum

20.

Most of the time, modification anomalies are serious enough that tables should be normalized into:

A.1NF.
B.2NF.
C.3NF.
D.BCNF.

Answer: D

Correct answer: BCNF.

Boyce-Codd Normal Form requires every determinant to be a candidate key, and a table satisfying it is free of the anomalies that arise from functional dependencies. Third normal form leaves some cases unhandled, which is why BCNF rather than 3NF is the practical target. Beyond it, 4NF deals with multivalued dependencies, which are a separate matter.

Discuss in Forum

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