Ch 6

Question 1

Normalization

Answer 1

Normalization is a process for evaluating and correcting table structures to minimize data redundancies, thereby reducing the likelihood of data anomalies.

Question 2

Denormalization

Answer 2

Denormalization produces a lower normal form; that is, a 3NF will be converted to a 2NF through denormalization. Denormalization is sometimes needed to meet performance requirements.

Question 3

Partial dependency

Answer 3

A partial dependency exists when there is a functional dependence in which the determinant is only part of the primary key (remember the assumption that there is only one candidate key).

Question 4

Transitive dependency

Answer 4

A transitive dependency exists when there are functional dependencies such that X –> Y, Y –> Z, and X is the primary key. In that case, X –> Z is a transitive dependency because X determines the value of Z via Y.

Question 5

Repeating group

Answer 5

A repeating group derives its name from the fact that a group of multiple entries of the same type can exist for any single key attribute occurrence.

Question 6

Dependency diagram

Answer 6

Diagrams that depict all the dependencies found within a table structure is known as a dependency diagram.

Question 7

1NF (first normal form)

Answer 7

The term first normal form (1NF) describes the tabular format in which:

1. All of the key attributes are defined.
2. There are no repeating groups in the table. In other words, each row/column intersection contains one and only one value, not a set of values.
3. All attributes are dependent on the primary key.

Question 8

2NF (second normal form)

Answer 8

A table is in second normal form (2NF) when:

1. It is in 1NF, and,
2. It includes no partial dependencies; that is, no attribute is dependent on only a portion of the primary key.

It is still possible for a table in 2NF to exhibit transitive dependency; that is, the primary key may rely on one or more nonprime attributes to functionally determine other nonprime attributes, as indicated by a functional dependence among the nonprime attributes.

Question 9

Determinant

Answer 9

A determinant is any attribute whose value determines other values within a row.

Question 10

3NF (third normal form)

Answer 10

A table is in third normal form (3NF) when:

1. It is in 2NF, and,
2. It contains no transitive dependencies.

Question 11

Atomic attribute

Answer 11

An atomic attribute is one that cannot further be subdivided. Such an attribute is said to display atomicity.

Question 12

Granularity

Answer 12

Granularity refers to the level of detail represented by the values stores in a table’s row. Data stored at their lowest level of granularity are said to be atomic data.

Question 13

Boyce-Codd normal form (BCNF)

Answer 13

A table is in Boyce-Codd normal form (BCNF) when every determinant in the table is a candidate key.