Database Reference
In-Depth Information
ing (
OLTP
) scenarios, that is, in situations where there is a need to collect, modify, and
maintain data on a daily basis. The type of data stored in an operational database is dy-
namic, meaning that it changes constantly and always reflects up-to-the-minute informa-
tion. Organizations such as retail stores, manufacturing companies, hospitals and clinics,
and publishing houses use operational databases because their data is in a constant state of
flux.
In contrast, analytical databases are primarily used in online analytical processing (
OLAP
)
scenarios, where there is a need to store and track historical and time-dependent data. An
analytical database is a valuable asset when there is a need to track trends, view statistical
data over a long period of time, and make tactical or strategic business projections. This
type of database stores static data, meaning that the data is never (or very rarely) modified.
The information gleaned from an analytical database reflects a point-in-time snapshot of
the data. Chemical labs, geological companies, and marketing analysis firms are examples
of organizations that use analytical databases.
Analytical databases often use data from operational databases as their main data source,
so there can be some amount of association between them; nevertheless, operational and
analytical databases fulfill very specific types of data processing needs and creating their
structures requires radically different design methodologies. This topic focuses on design-
ing an operational database because it is still the most commonly used type of database in
the world today.
Early Database Models
In the days before the relational database model, two data models were commonly used to
maintain and manipulate data—the
hierarchical database model
and the
network database
model.
Note
I'veprovidedabriefoverviewofeachofthesemodelsforhistoricalpurposesonly.
In an overall sense, I believe it is useful for you to know what preceded the rela-
tional model so that you have a basic understanding of what led to its creation and
evolution.
In the following overview I briefly describe how the data in each model is struc-
tured and accessed, how the relationship between a pair of tables is represented,
and one or two of the advantages or disadvantages of each model.
Some of the terms you'll encounter in this section are explained in more detail in
Chapter
3
,
“
Terminology
.
”
