Chapter 6 Database Systems

From a structural point of view, 2NF is better than ____.

1NF

Data warehouse routinely uses _____ structures in its complex, multilevel, multisource data environment. 1NF 2NF 3NF 4NF

2NF

From a structural point of view, 3NF is better than _____. 2NF 3NF 5NF 6NF

2NF

A table that is in 2NF and contains no transitive dependencies is said to be in _____. 1NF 2NF 3NF 4NF

3NF

For most purposes in business database design, _____ is as high as you need to go in the normalization process.

3NF

A table where all attributes are dependent on the primary key but are independent of each other, and no row contains two or more multivalued facts about an entity is said to be in _____. 1NF 2NF 3NF 4NF

4NF

In the _____, no row may contain two or more multivalued facts about an entity.

4NF

Some very specialized applications may require normalization beyond the _____. 1NF 2NF 3NF 4NF

4NF

Explain the Boyce-Codd normal form (BCNF). How is it related to other normal forms?

A table is in Boyce-Codd normal form (BCNF) when every determinant in the table is a candidate key. A candidate key has the same characteristics as a primary key, but for some reason, it was not chosen to be the primary key. Clearly, when a table contains only one candidate key, the 3NF and the BCNF are equivalent. In other words, BCNF can be violated only when the table contains more than one candidate key. Most designers consider the BCNF to be a special case of the 3NF. In fact, if the techniques shown in this chapter are used, most tables conform to the BCNF requirements once the 3NF is reached.

When designing a new database structure based on the business requirements of the end users, the database designer will construct a data model using a technique such as _____.

Crow's Foot notation ERDs

Of the following normal forms, _____ is mostly of theoretical interest. 1NF 3NF BCNF DKNF

DKNF

_____ databases reflect the ever-growing demand for greater scope and depth in the data on which decision support systems increasingly rely. Normalized Data warehouse Temporary Report

Data warehouse

____ yields increased performance in a database system.

Denormalization

A dependency of one nonprime attribute on another nonprime attribute is a partial dependency

F

Dependencies that are based on only a part of a composite primary key are called transitive dependencies.

F

Normalization purity is often easy to sustain in the modern database environment.

F

Since a partial dependency can exist only if a table's primary key is composed of several attributes, if a table in 1NF has a single-attribute primary key, then the table is automatically in 2NF.

F

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

Normalization

A table is in fourth normal form if it is in third normal form and has no independent multivalued dependencies.

T

All relational tables satisfy the 1NF requirements.

T

In order to meet performance requirements, portions of the database design may need to be occasionally denormalized.

T

In the context of partial dependencies, data redundancies occur because every row entry requires duplication of data.

T

It is possible for a table in 2NF to exhibit transitive dependency, where the primary key may rely on one or more nonprime attributes to functionally determine other nonprime attributes.

T

Normalization represents a micro view of the entities within the ERD.

T

Normalization works through a series of stages called normal forms.

T

Relational models view data as part of a table or collection of tables in which all key values must be identified.

T

Repeating groups must be eliminated by ensuring that each row defines a single entity.

T

The combination of normalization and ER modeling yields a useful ERD, whose entities can be translated into appropriate table structures.

T

Normalization works through a series of stages called normal forms. From a structural point of view, 2NF is better than 1NF, and 3NF is better than 2NF. However, you will discover that properly designed 3NF structures also meet the requirements of fourth normal form (4NF). T or F

True

A table that displays data redundancies yields ____.

anomalies

The normalization process involves _______ attributes to tables based on the concept of determination.

assigning

Improving _____ leads to more flexible queries. atomicity normalization denormalization derived attribute

atomicity

BCNF can be violated only if the table contains more than one _____ key. primary candidate foreign secondary

candidate

In a(n) _____ diagram, the arrows above the attributes indicate all desirable dependencies. Chen dependency functionality ER

dependency

From a system functionality point of view, _____ attribute values can be calculated when they are needed to write reports or invoices. derived atomic granular historical

derived

Any attribute whose value determines other values within a row is known as a(n) _____.

determinant

According to the data-modeling checklist, _____ should be nouns that are familiar to business, should be short and meaningful, and should document abbreviations, synonyms, and aliases for each entity.

entity names

Normalization works through a series of stages called normal forms. The first stages is described as _____

first normal form (1NF)

In a real-world environment, we must strike a balance between design integrity and _____. robustness flexibility uniqueness ease of use

flexibility

It becomes difficult to create a suitable _____ key when the related table uses a composite primary key.

foreign

_____ refers to the level of detail represented by the values stored in a table's row.

granularity

An ERD is created through a(n) _____ process.

iterative

In a _____ situation, one key determines multiple values of two other attributes and those attributes are independent of each other. multivalued dependency transitive dependency partial dependency functional dependency

multivalued dependency

Normalization works through a series of stages called _____ forms.

normal

The combination of _____ and ER modeling yields a useful ERD, whose entities may now be translated into appropriate table structures.

normalization

The most likely data type for a surrogate key is _____. character date logical numeric

numeric

Dependencies based on only a part of a composite primary key are known as _____ dependencies. primary partial incomplete composite

partial

A dependency based on only a part of a composite primary key is called a(n) _____.

partial dependency

In order to meet _____ requirements, you may have to denormalize some portions of a database design.

performance

Because a partial dependency can exist only when a table's primary key is composed of several attributes, a table whose _____ key consists of only a single attribute is automatically in 2NF once it is in 1NF.

primary

An attribute that is part of a key is known as a(n) _____ attribute. important nonprime prime entity

prime

Any attribute that is at least part of a key is known as a(n) _____.

prime attribute (key attribute)

Normalization works through a series of stages called normal forms. The second stages is described as _____

second normal form (2NF

In a real-world environment, changing granularity requirements might dictate changes in primary key selection, and those changes might ultimately require the use of _____ keys.

surrogate

An example of denormalization is using a _____ denormalized table to hold report data. This is required when creating a tabular report in which the columns represent data that are stored in the table as rows. transitive 3NF component temporary

temporary

Granularity refers to _____. the size of a table the level of detail represented by the values in a table's row the number of attributes represented in a table the number of rows in a table

the level of detail represented by the values in a table's row

Normalization works through a series of stages called normal forms. The third stages is described as _____

third normal form (3NF)

Normalization works through a series of stages called normal forms. For most purposes in business database design, _____ stages are as high as you need to go in the normalization process. two three four five

three

A(n) _____ exists when there are functional dependencies such that Y is functionally dependent on X, Z is functionally dependent on Y, and X is the primary key. partial dependency repeating group atomic attribute transitive dependency

transitive dependency

Unnormalized tables yield no simple strategies for creating virtual tables known as _____.

views