Database Reference
In-Depth Information
Structure-Related Terms
Table
are perceived by the user as
tables.
Each relation is composed of
tuples
(records) and
at-
tributes
(fields).
Figure 3.6
shows a typical table structure.
Figure 3.6. A typical table structure
Tables are the chief structures in the database and each table always represents a single,
specific subject. The logical order of records and fields within a table is of absolutely no
importance, and every table contains at least one field—known as a
primary key
—that
key of the CLIENTS table.) In fact, data in a relational database can exist independently of
the way it is physically stored in the computer because of these last two table characterist-
ics. This is great news for the user because he or she isn't required to know the physical
location of a record in order to retrieve its data.
The subject that a given table represents can either be an
object
or an
event.
When the sub-
ject is an object, it means that the table represents something that is tangible, such as a
person, place, or thing. Regardless of its type, every object has characteristics that you can
store as data and then process as information in an almost infinite number of ways. Pilots,
products, machines, students, buildings, and equipment are all examples of objects that a
table can represent, and
Figure 3.6
illustrates one of the most common examples of this
type of table.
