Entity and Entity Relationship model



JavaScript Dev

ER or Entity Reletionship model is used to create and model the data which is simple, non technical and easily understood by people describing a diagram with relation. It helps us to analyze requirements systematically to produce a well designed database.

ER diagram

It is a visual representation of entity and attributes also it helps us to show relationships between entities . Symbols and connectors are used to indicate the relation between entities or describe information using symbols and connectors.

Entity type: It defines a collection of similar entities.

Types of entity type are as follows:

  • Strong entity: Strong entity means an entity which has primary key and it doesn’t depend on other entities for existence. It is also known a parent entity.
  • Weak entity: Weak entity means an entity which doesn’t have key attributes of their own.
  • Composite entity: Composite entity is used to make a Many to Many relationship between 2 or more entities. This entity is composed of primary keys from each of the connected entities.
  • Recursive entity: When an entity has a relation with same entity it is called recursive entity.