Entity-Relationship Model. Relationships
Relationships in Databases
In relational databases, various relationships can be illustrated in diagrams.
![](https://codefinity-content-media-v2.s3.eu-west-1.amazonaws.com/courses/5ac24d9d-4a16-45b3-8856-07dec028c5e9/Section+1/ERM_relation_intro%404x-8.png)
Different entities can have specific interdependencies, each defining how elements interact. An element might relate to multiple others or just one. This interaction is termed a relationship.
Relational databases capture these connections in diagrams.
Types of Relationships:
- One-to-One;
- One-to-Many;
- Many-to-One;
- Many-to-Many.
We'll dive deeper into these relationship types later, but for now, here's their representation:
Mandatory vs. Optional Relationships
Mandatory and optional relationships come with distinct markers: | (a line) for mandatory and o (a circle) for optional.
- A mandatory relationship implies that a particular entity instance must have a connection to another entity;
- An optional relationship means that an entity instance might have a link to another entity, but it's not obligatory.
Consider the following examples:
While mandatory and optional relationships might not be frequently used, it's crucial to recognize these markers.
Select all relationship types:
Selecciona unas respuestas correctas
¿Todo estuvo claro?
Contenido del Curso
Relational Database and Normalization
3. Normalization and Normal Forms
Relational Database and Normalization
Entity-Relationship Model. Relationships
Relationships in Databases
In relational databases, various relationships can be illustrated in diagrams.
![](https://codefinity-content-media-v2.s3.eu-west-1.amazonaws.com/courses/5ac24d9d-4a16-45b3-8856-07dec028c5e9/Section+1/ERM_relation_intro%404x-8.png)
Different entities can have specific interdependencies, each defining how elements interact. An element might relate to multiple others or just one. This interaction is termed a relationship.
Relational databases capture these connections in diagrams.
Types of Relationships:
- One-to-One;
- One-to-Many;
- Many-to-One;
- Many-to-Many.
We'll dive deeper into these relationship types later, but for now, here's their representation:
Mandatory vs. Optional Relationships
Mandatory and optional relationships come with distinct markers: | (a line) for mandatory and o (a circle) for optional.
- A mandatory relationship implies that a particular entity instance must have a connection to another entity;
- An optional relationship means that an entity instance might have a link to another entity, but it's not obligatory.
Consider the following examples:
While mandatory and optional relationships might not be frequently used, it's crucial to recognize these markers.
Select all relationship types:
Selecciona unas respuestas correctas
¿Todo estuvo claro?