Entity Relationship Model

Entity Relationship Model

1. What is it?

   • It is a type of flowchart that illustrates how "entities", such as people, objects, or concepts, relate to each other within a system.
   • Components of the ER Diagram
     • Entities
       • Entities represent things or objects (either real or abstract), which are clearly distinct from each other.
     • Attributes
       • Attributes define or identify the characteristics of the entity (it is the content of this entity).
     • Relationships
       • It is a link that allows us to define a dependency between several entities, that is, it allows us to require that several entities share certain attributes in an essential way.

2. symbols in ER Diagrams

   • • Rectangles: This Entity Relationship Diagram symbol represents entity types • Ellipses : Symbol represent attributes • Diamonds: This symbol represents relationship types • Lines: It links attributes to entity types and entity types with other relationship types • Primary key: attributes are underlined • Double Ellipses: Represent multi-valued attributes
     • How to Create an Entity Relationship Diagram (ERD)
       • Step 1) Entity Identification
         • Step 2) Relationship Identification
           • Step 3) Cardinality Identification
             • Step 4) Identify Attributes
               • Step 5) Create the ERD Diagram

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