What ia an ERD. Define the RED related terms, including entities, attributes, cardinalities and relationships

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 ERD:

An entity-relationship diagram (ERD) is a data modeling technique that graphically illustrates an information system’s entities and the relationships between those entities. An ERD is a conceptual and representational model of data used to represent the entity framework infrastructure.(Entity-Relationship Diagram ERD ,2011)

Steps involved in creating an ERD include:

  1. Identifying and defining the entities
  2. Determining all interactions between the entities
  3. Analyzing the nature of interactions/determining the cardinality of the relationships
  4. Creating the ERD.  (Entity-Relationship Diagram ERD ,2011
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The ERD related terms are:

1. Entity:  
An entity is an object or concept about which you want to store information. A weak entity is an entity that must defined by a foreign key relationship with another entity as it cannot be uniquely identified by its own attributes alone.They are represented by rectangles.(Entity Relationship Diagram ERD)

2.Attribute:
A key attribute is the unique, distinguishing characteristic of the entity. For example, an employee's social security number might be the employee's key attribute.
A multivalued attribute can have more than one value. For example, an employee entity can have multiple skill values. A derived attribute is based on another attribute. For example, an employee's monthly salary is based on the employee's annual salary.They are represented by ovals.(Entity Relationship Diagram ERD)

3. Cardinality :
A cardinality specifies the numerical attribute of the relationship between entities. It can be one-to-one, many-to-one, or many-to-many.(Entity Relationship Diagram ERD)

4. Relationships:
It shows how two entities share information in the database. In some cases, entities can be self-linked. They are represented by diamond shapes.(Entity Relationship Diagram ERD)



Reference:

Entity-Relationship Diagram (ERD) (2011) Techopedia.com. What is an Entity-Relationship Diagram (ERD)? - Definition from Techopedia. Available at: https://www.techopedia.com/definition/1200/entity-relationship-diagram-erd (Accessed: February 26, 2023).

Entity Relationship Diagram (ERD) Smartdraw.com. Available at: https://www.smartdraw.com/entity-relationship-diagram/ (Accessed: February 26, 2023).

Entity Relationship Diagram (ERD) Smartdraw.com. Available at: https://www.smartdraw.com/entity-relationship-diagram/ (Accessed: February 26, 2023).




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