Relational Data Model:
Relational data model is the most commonly used
data model to design the database. In 1970, Dr. Codd gave the concept of
relational data model, while he was working as a researcher at IBM. The
relational data model is based on the mathematical theory, and therefore, has a
solid theoretical foundation. This model represents a database as collection of
relations, which are physically represented as tables or two-dimensional arrays.
Similarly, the attributes are represented by columns of table and each row in a
table represents a collection of related data values for a particular instance
of an entity.
The relational data model consists of the
following three components.
(i) Data Structure: Data of various types can be organized in the form
of tables or relations.
(ii) Data Manipulation: Powerful operations can
be performed to manipulate data stored in the relations.
(iii) Data Integrity: Data integrity rules can be
applied to maintain data accuracy and data validity.
A database that contains multiple tables to store
data and relationships can be created on the common fields of tables, is called
relational database. The data in relational database is stored in tables. In
relational database, table is the basic structure in which data is stored.
Suppose a college database has two tables 'Student' and 'Marks'. The tables with
sample data are given below;
In the above tables, the association between tables can be created logically by
the values that are stored within the columns of the tables. For example, the
roll numbers of students are stored in both tables in the column heading
'Roll-No'. A relationship can be created between two tables on the common column
'Roll-No'. In this way data can be linked between two tables.
In the past 20 years, most of the commercial
database systems have been developed following the relational data model and
therefore, are relational database systems. INGRES was an early relational data
model developed at the University of California.
A relational database system provides various
operations used to manipulate the data in the database tables. The data
retrieved (output returned by RDBMS) from relational database is also presented
in the form of table. For example, the database access language provides a way
to select data that meets a certain criteria from one or more tables of
database. Note that the rows extracted can themselves be presented in the form
Relational Data Model Advantages
The relational data model provides several
advantages, but the main advantages are;
- It allows for developing simple but powerful
structure for databases.
- It allows separation of the logical and
physical level, so that logical design can be performed without considering
the storage structures.
- It allows for designing or expressing the
data of an organization in a simple way, which can easily be understood.
- The data operations can easily be expressed
in a simple way.
- It allows for applying data integrity rules
on the relations of database.
- Data from multiple tables can be retrieved
- It allows users for inserting, modifying,
and deleting the rows in a table without facing any problems.