Entity Relationship Model (ER model) in DBMS

Entity-Relationship model (ER model)


  • An effective system where data is organized into discrete categories called entities(different database tables) 
  • ERmodel is an illustration of various entities in business and the relationship between them 
  • It is built during the analysis phase of the system development life cycle 
  • The ER model separates the information required in the business i.e it establishes a clear distinction between data that is useful and not useful for business operations 
Entity Relationship Data Models in DBMS


Key components of the ER model 

Entity : 

 It is a set of related information i.e nothing but a database table.


Attributes : 
    •  It defines what type of data an entity is storing i.e different columns in a table 
    • For example, a student entity consists of student name, ID, marks as attributes
    • An entity may contain any numbers of attribute but it must contain at least one attribute .


Relationships :
    • It is defined as an association between entities links between different database tables for data accessing 
    • Several relationships may exist between the same entity basically 4 relationships are identified
      • One to one
      • One to many
      • Many to one
      • Many to many 
    • These relationships are nothing but the links between in a table to another table or set of tables so that data can be  transferred and used from more than one table .


ER model benefits 

  • Provide a clear picture of the scope of information requirement 
  • Provides an easily understandable pictorial map for database design 
  • It offers an effective Framework for integrating multiple applications.