What is ER-Model (Entity-Relationship Model & Entity-Relationship Diagram)

Entity Relationship Model (ER-Model) :

Definition : The ER model defines the conceptual view of a database. The entity-relationship model is a way of graphically representing the logical relationships of entities (or objects) in order to create a database.ER modeling is a top-down structure to database design that begins with identifying the important data called entities and relationships in combination between the data that must be characterized in the model. Then database model designers can add more details such as the information they want to hold about the entities and relationships which are the attributes and any constraints on the entities, relationships, and attributes. ER modeling is an important technique for any database designer to master and forms the basis of the methodology.

ER-Diagrams : ER-Diagram is a pictorial representation of data that describes how data is communicated and related to each other. Any object, such as entities, attributes of an entity, sets of relationship and other attributes of relationship can be characterized with the help of the ER diagram. In ER diagram, the structure for a database is portrayed as a diagram, that resembles the graphical breakdown of a sentence into its grammatical parts. Entities are rendered as points, polygons, circles, or ovals. Relationships are portrayed as lines connecting the points, polygons, circles, or ovals. ER diagram basically breaks requirement into entities, attributes and relationship. For example below given diagram is the E-R diagram of Library Management System.

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Entity-Relationship Model : Entity, Entity-Sets and Entity Types
RDBMS Full List

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