According to Wikipedia, the
definition of Relational Database is “is a digital database whose organization
is based on relational model of data, as proposed by E.F. Codd in 1970. ” [1]. There are many
important terms associated with relational database theory. For instance,
relational model is a database model “based on first-order predicate logic.”
[2] In the model, all data are represented by tuples (rows) and attributes
(columns). A tuple is an ordered list of elements while attribute
can be renamed to any characteristic information (ie. Name) and categorizes all
the same features. Here is an example
database according to Relational Model:
Figure 1: An example
database
In the relational database, each entity is given
with a unique key that can be linked to when used in other table as well. By
storing this key into another row in a different table, the information of this
entity can be represented and declared in other table. This is particularly
helpful when a massive variety of data is stored, the user can still find the
data they want by letting the system find the links (aka. relation) between different
data. As a result, “data relationships of arbitrary complexity can be
represented using this simple set of concepts” as Codd argued.
The official descriptive definition of this kind
of relation is “procedural relational algebra query language or its equivalent
declarative relational calculus”. [3] . Below is a demonstration of the
expression of relational algebra describing the how this relation works in
database:
Figure 2: Example of Relational Algebra
As society develops, more and more data are being
stored in various kinds of database. The invention of relational database is
particularly helpful in regards with the pratical need for efficient
manipulation of large amounts of structured information.
[2] http://en.wikipedia.org/wiki/Relational_model
[3] Elements of Relational Database Theory, Paris C.
Kanellakis, 1989
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