Hi there,
There are several reasons why the relational data model has become the
most common one for use in databases, the main one being that it is
demonstrably superior in many respects to the previous data models
that were employed in database construction. It is also widely
acknowledged and understood to be so.
To understand why the relational model has largely supplanted previous
models it is necessary to briefly look at what the previous models
were, and the problems that they had that the relational model
addressed.
For starters, previous databases were flat. This means that the
information was stored in one big text file, often called a tab
delimited file. Each entry in the tab delimited file was separated by
a special character, such as a vertical bar (|). Each entry contained
multiple pieces of information (fields) about a particular object or
person grouped together as a record.
This text file format made it difficult to search for specific
information or to create reports that included only certain fields
from each record. You would, for example, have to search sequentially
through an entire database of employee information to generate a
report about their salaries (assuming that 'salary' was an information
field that all the employee records in question contained).
Along with other previously employed models such as 'hierarchical' and
'network' models, the basic problem with flat databases was that
people working with one had to have an understanding of how the data
was structured within it in order to retrieve, insert, update, or
delete records from the database.
In 1970, when E.F. Codd developed the relational database model, it
could be seen to be a great improvement over previous models. At the
core of the then-new relational model was the concept of a table (also
called a relation) in which all data is stored. Each table is made up
of records (horizontal rows also known as tuples) and fields (vertical
columns also known as attributes). It is important to note that how or
where the tables of data are stored made no difference. Each table
could be identified by a unique name and that name could be used by
the database to find the table behind the scenes. As a user, all you
had to know was the table name in order to use it. You would not need
to worry as you did previously about the complexities of how the data
is stored on the hard drive.
The structure of a relational database also allowed sorting based on
any field and the generation of reports that contain only certain
fields from each record. A relational database uses the relationship
of similar data to increase the speed and versatility of the database.
This data access methodology made the relational model a lot different
from and better than the earlier database models because it was a much
simpler model to understand and work with. This is another
widely-cited reason for the popularity of relational database systems
in the world today.
In addition to being relatively easy to create and access, a
relational database also had the important advantage of being easy to
extend. After the original database creation, a new data category
could be added without requiring that all existing applications be
modified (such as would normally be required with flat file databases,
for example).
Another benefit of the relational system is that it provided extremely
useful tools for database administration. Essentially, tables can not
only store actual data but they can also be used as the means for
generating meta-data (data about the table and field names which form
the database structure, access rights to the database, integrity and
data validation rules etc).
Lastly, along with the development of the relational data model came
the development of SQL (Structured Query Language, a database query
language). SQL is relatively easy to learn, has been adopted as an
industry-wide standard since 1986, and allows people to quickly
develop the capability to query and modify a relational database. The
straightforwardness and simplicity of manipulation that SQL permits is
another part of the reason that relational databases now form the
majority of databases to be found.
Thank you for using Google Answers. Please feel free to request
additional clarification from me if you do not feel this response
adequately answers your query.
Search queries used:
://www.google.com/search?q=popularity+of+relational+databases
://www.google.com/search?q=relational+data+model+superiority
://www.google.com/search?q=what+is+sql
Regards,
-dakur-ga |
