DBMS > Data Model > What is Relational Data Model?

Relational Model

This model was initially described by Edgar F. Codd, in 1969. The relational data model is the widely used model which is primarily used specially in commercial data processing applications.  In this model, the data is maintained in the form of a two-dimensional table. All the information is stored in the form of row and columns. So A relational model uses tables for representing data and in-between relationships and tjese the tables are also called relations in the relational model.

 

In this example, we have an Student table. 

 

Student Id	S_Name	Contact
1	Orpita Das	01922999217
2	Raihan	01922345686
3	Naima Ferdowse	01935476667

Features of Relational Model

• Tuples: Each row in the table is called tuple. A row contains all the information about any instance of the object. In the above example, each row has all the information about any specific individual like the first row has information about Orpita Das.
• Attribute or field: Each column in a table is called attribute. Attributes are the property which defines the table or relation. The values of the attribute should be from the same domain.

• Primary Key: A field or attribute that uniquely identifies each row (tuple) of a table.

  Foreign Key: Unlike primary key, a foreign key in one table is a reference to a primary key in another table. A foreign key matches a primary key in another table and is what allows the tables to be joined or related.

  Composite Key/Compound Key/Concatenated Key: A primary or foreign key that consists of more than one fields or attributes. A composite key is sometimes created if a table has no single field that can uniquely identify every record in the table, but if two or more fields are combined, the result can be such a key.

Advnatages of Relational Model

• Simple: This model is more simple as compared to the network and hierarchical model.
• Scalable: This model can be easily scaled as we can add as many rows and columns we want.
• Structural Independence: We can make changes in database structure without changing the way to access the data. 

Disadvantages of Relatinal Model

• Hardware Overheads: For hiding the complexities and making things easier for the user this model requires more powerful hardware computers and data storage devices.
• Bad Design: As the relational model is very easy to design and use. So the users don't need to know how the data is stored in order to access it. This ease of design can lead to the development of a poor database which would slow down if the database grows.

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