Relational database theory refers to databases built around
a collection of related tables, known as relations. Each relation is made up of a series of
related data which is stored in rows and columns. The relational model for database management
was proposed by Edgar F. Codd in 1969, and was designed to provide a
declarative method for specifying data and queries. This means that the users of the database directly
state what information the database contains and what they want it to retrieve
for them. The database’s software will
then take care of describing the data structure and retrieving the information
for the user.
Relational databases are designed to use a certain data
type, which can include a set of integers, character strings, a set of dates,
true or false, or any number of user defined data types. A tuple
in a relational database is basically a row, and the data in a tuple is
referred to in the database by its attribute name. The equivalent of a column in the database is
the attribute, and its data is
referred to by the attribute value.
Together, attributes and tuples hold data which makes up the relation’s
body, along with the heading, which is the structure definition for the
table.
Almost all relational databases currently in use, use
Structured Query Language (SQL) as the language for querying and maintaining
the database, which does not strictly follow the relational model, but still
uses many of the same concepts. Also,
although SQL was developed for use by the end-users of the databases, many
programs have software which will embed the SQL queries for the data users are trying
to access, making it much simpler for lay-people to use and access the data
contained within databases. One example
of this happening is searching Wikipedia.
When a search term is typed into the search bar, Wikipedia embeds the
data in SQL and uses it to retrieve the correct data from its servers to
display.
Comments:
Kaili Yue – I thought it would be interesting to hear more
about the development of databases at IBM and how they have progressed since
the DB2 in 1983.
Catherine Stephens – You talk about the terms relation and
table not being synonymous, however, because relation model is only theoretical
and the relational databases are only based off of it, I feel that they are
both synonymous, since they do perform many of the same functions and could
certainly be compared to one another.
Sources:
Wikipedia contributors.
"Relational model." Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 28 Nov. 2014. Web. 10
Feb. 2015.
Wikipedia contributors.
"Relational database." Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 2 Feb. 2015. Web. 10 Feb.
2015.
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