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# Relational Data Model:

## Definition Explanation

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;

 Student Table Marks Table Roll_No Name City Roll_No Phy Math Comp 1 S L 1 86 58 86 2 K P 2 78 75 78 3 F Q 3 96 74 54 4 H L 4 54 76 78

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 of table.

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 very easily.
• It allows users for inserting, modifying, and deleting the rows in a table without facing any problems.

## Relevant Articles:

 Logical Database Design Relational Data Model Relation in database (DBMS) Data Integrity Rules Relational Data Manipulation Languages Relational Algebra Operators in DBMS Codd's 12 Rules For the Relational Model

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