Difference between E-R Model and Relational Model in DBMS
Last Updated :
25 Sep, 2024
In database management systems (DBMS), two key methods are the Relational model and the Entity-Relationship (E-R) model. Each has a specific function in the development and operation of databases. While the Relational model provides the practical structure for organizing and managing data in relational databases, the E-R model concentrates on offering a conceptual framework for comprehending the relationships between entities.
The E-R model and the Relational model are two types of data models present in DBMS. Let's have a brief look at them:
What is the E-R Model?
The E-R model stands for the Entity-Relationship model. ER Model is used to model the logical view of the system from a data perspective which consists of these components: Entity, Entity Type, Entity Set. An Entity may be an object with a physical existence – a particular person, car, house, or employee – or it may be an object with a conceptual existence – a company, a job, or a university course. An Entity is an object of Entity Type and a set of all entities is called an entity set. e.g.; E1 is an entity having Entity Type Student and a set of all students is called Entity Set. An Entity Type defines a collection of similar entities and a set of all entities is called an entity set.
What is the Relational Model?
The Relational Model was proposed by E.F. Codd to model data in the form of relations or tables. After designing the conceptual model of the Database using an ER diagram, we need to convert the conceptual model into a relational model that can be implemented using any RDBMS language like Oracle SQL, MySQL, etc. Consider a relation STUDENT with attributes ROLL_NO, NAME, ADDRESS, PHONE, and AGE shown in Table 1.
STUDENT
| ROLL_NO | NAME | ADDRESS | PHONE | AGE |
| 1 | RAM | DELHI | 9455123451 | 18 |
| 2 | RAMESH | GURGAON | 9652431543 | 18 |
| 3 | SUJIT | ROHTAK | 9156253131 | 20 |
| 4 | SURESH | DELHI | | 18 |
Differences Between ER Model and Relational Model
Let’s see the difference between ER model and relational model:
| ER model | Relational model |
|---|
| Developed by Peter Chen in 1976. | Developed by E.F. Codd in 1970. |
| ER model is the high level or conceptual model. | It is the representational or implementation model. |
| It is used by people who don't know how database is implemented. | It is used by programmers. |
| It represents collection of entities and describes relationship between them. | It represent data in the form of tables and describes relationship between them. |
| It consists of components like Entity, Entity Type, Entity Set. | It consists of components like domain, attributes, tuples. |
| It is easy to understand the relationship between entities. | It is less easy to derive the relationship between different tables. |
| It describes cardinality. | It does not describe cardinality. |
| E-R model does not define data dependencies. | Relational model defines dependencies in tables. |
| E-R model represents relationships as associations. | Relational model represents relationships as join tables. |
| E-R model is more granular in terms of data representation. | Relational model is less granular. |
| E-R model is more flexible than the relational model. | Relational model is less flexible than E-R model. |
| E-R model does not involve normalization. | Relational model involves normalization. |
| E-R model use case is useful for initial planning and design. | Relational model use case is useful for implementation and maintenance |
Some of the popular Language and Notations used- - Chen
- UML
- Crow's foot
- Bachman and others.
| Some of the popular Language and Notations used-
|
Conclusion
The Relational model is a practical implementation that uses tables for data storage, whereas the E-R model is a high-level conceptual tool for visualizing entities and relationships. Relational offers the framework for database systems, combining conceptual clarity with effective implementation, whereas E-R helps with design.
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