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

 

On this blog we will be find out what is ERD related terms, including enttities, attributes, cardinalities and relationship.

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An Entity-Relationship Diagram (ERD) is a visual representation of the structure and organization of data within a database system. ERDs are commonly used in database design to illustrate how diffrent entities are related to each other and how data is organized.(Peterson, 2023)

Terms related to ERDs:

Entities: are objects, concepts, or things in the real world that are represented in the database. each entity in an ERD is typically shown as a rectangle or a table and corresponds to a table in a relational database. Examples of entities could be "Custumer, Product, Employee or Order"

Attributes: are characteristics or properties of entities. They describe the data that is associated with an entity. Attributes are offten shown as olves or columns inside the entitity rectangle. For example for a Custumer entity, attributes might include Custumer ID Name Email and Phone Number.

Cardinalities: define the relationship between entities and specify how many instances of one entity are related to another entity. Cardinalities are represented using notations like "1" (one) :M"(Many) or "0" (zero)

One-to One (1:1) A single instance of one entity is associated with a single instance of another entity

One-to-Many (1:M) A single instance of entity can be related to multiple instances of another entity.

Many-to-One (M:1) Multiple instances of one entity can be related to a single instance of another entity.

Many-to-Many(M:M) Multiple instances of one entity can be related to multiple instances of another entity.

Relationships: represent how entities are connected or related to each other witin the database. Relationships are typically depicted as lines connecting the entities, and they have names that describe the nature of the relationship, such as "Owns, Works For or Purcharse Fom"

Refferences:

Entity relationship diagram (ERD) (no date) Entity Relationship Diagram (ERD) - What is an ER Diagram? Available at: https://www.smartdraw.com/entity-relationship-diagram/ (Accessed: 06 September 2023).

Peterson, R. (2023). Entity Relationship (ER) Diagram Model with DBMS Example. Guru99. https://www.guru99.com/er-diagram-tutorial-dbms.html