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12.3.1.3 Relational Data Model

The most popular data model in DBMS is the relational model. It is a more scientific and stable
model than hierarchical or network model since there are no pointers involved with the records,
and in case of any fault or error these pointers may result in inconsistency among the records and
can lead to reduced data integrity.
In this model, data is organized in two-dimensional tables called relations. The tables or relations
are related to each other. A relational database is based on this relational model developed by
E.F. Codd. In this type of database, the data and relations between them are organized into tables,
having logically related records containing the same fields. The contents of a table or relation can
be permanently saved for future use. Thus, this model is simple and has all the properties and
capabilities required to process data with storage efficiency.
A relational model consists of a collection of tables, each of which is assigned a unique name, i.e., it
represents the database as a collection of relations or tables. Characteristics of relational database
are:-

1. Data is conceptually represented as an orderly arrangement of data into rows and columns,
termed as a relation.

2. Each relation is represented as a table.
3. Columns described in a table are the attributes that belong to an entity which is modelled as a
table.

4. Every row in a table represents a single entity.
5. All the values in a relation are scalar, i.e., at any given row or column position, there is one and
only one value.

6. All operations are performed on the entire relation and the result is an entire relation.

Advantages of a relational model are as follows:
1. A relational model provides structural independence by using independent tables.
2. Changes made in the table structure do not affect the data access or other application programs.

3. It is represented in the form of tables; so, it is simple and easier to understand.
4. Tabular view also provides easier database design, use, implementation and management.

5. Built-in query support based on SQL is provided by RDBMS (Relational Database Management
System).
6. Data organization and manipulation is easy, flexible and faster.
Computer Science with Python–XII 12.8 8. Mathematical operations can be successfully carried out using RDBMS.
7. Powerful structure designing and processing capabilities of RDBMS isolate the end-user from
physical-level details and, thus, improve implementation and management simplicity.

The limitations of relational model are:
1. RDBMS incurs hardware and system software overheads.

2. The size of database becomes very large.