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Difference Between E-R Model and Relational Model in DBMS
In Database Management Systems (DBMS), the ways of designing databases at physical, logical, and view levels are referred to as Data Models. There are two popular data models− the ER Model and the Relational Model. The fundamental difference between the ER Model and the Relational Model is that the ER Model is an entityspecific data model, while the relational model is a table specific model.
Read this article to find out more about the ER Model and the Relational Model and how they are different from each other.
What is ER Model?
ER Model, short for Entity Relationship Model, is a data model that is based on the real−world entities and their relationships. ER models are normally represented by ER Diagrams. Thus, the ER Model makes it easy for the developers to understand the system by simply looking at the ER diagram. An ER diagram have three basic components namely Entity, Attributes, and Relationship.
An Entity is a real−world thing which can be a person, place, or even a concept. For example Admin, Department, Courses, Students, Teachers, Building, etc. are some of the entities of a School Management System. An attribute is an entity which contains a real−world property. For example, the entity employee has the property like employee Id, Salary, Age, Address, etc. Relationship provides information that how two attributes are related together. For example an employee works for a department.
What is Relational Model?
Relational data model is a primary data model that widely used around the world for data storage and processing. The relation model is so popular because it is quite simple and it has all the properties and capabilities that required to process data with storage efficiency. The relational model uses several concepts such as tables, tuples, relation instances, relation schema, relation key, and attribute domain. Now, let us try to briefly understand what these terms mean.
Tables − In a relational model, relations are saved in the form of Tables. The table stores the relation among entities. A table consists of rows and columns, where rows represent records and columns represent the fields/attributes.
Tuple − A tuple is a single row of a table that contains a single record for that relation.
Relation Instance − It is a finite set of tuples in the relational database management system. The relation instances do not have duplicate tuples.
Relation Schema − It describes the relation name (i.e. table name), attributes and their names.
Relation Key − Each row has one or more attributes that are known as relation keys. A relation key can identify the row in the table uniquely.
Attribute Domain − It is the predefined value scope that every attribute has.
Difference between E−R Model and Relational Model in DBMS
The following table highlights all the important differences between ER Model and Relational Model in DBMS −
|S. No.||ER Model||Relational Model|
|1.||It can be expanded as an entity relationship model.||It is a representational or implementation model.|
|2.||It is a high−level/conceptual model.||It is used by programmers to understand relationship between tables.|
|3.||It represents a collection of entities, and describes the relationship between these entities.||It represents the data in the form of tables.|
|4.||It is generally used to understand how a database would be implemented.||It also describes the relationship between these tables.|
|5.||It is easy to understand the relationship between entities.||It is not easy to understand/extract the relationship between multiple tables.|
|6.||It consists of components such as ‘Entity’, ‘Entity Type’, and ‘Entity Set’.||It consists of components such as ‘domain’, ‘attributes’, and ‘tuples’.|
|7.||It describes the cardinality of attributes.||It doesn’t describe the cardinality.|
From the above discussion, we may conclude the most significant difference between the ER Model and the Relational Model is that the ER Model represents a collection of entities and describes the relationship between these entities, whereas the Relational Model represents the data in the form of tables.
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