⛓ Entity Relationship modelling (ERD)

A type of diagram that lets you see how different entities (e.g. people, customers, or other objects) relate to each other in an application or a database.

It's used to represent data in a given scenario.
Entity relationship models have 3 components:
- Entities
- Attributes
- Relationships

Explanation

An entity is something in the real world that can be represented in the system. These could be: books, people, a bag etc...
Each entity is represented by a rectangular box with its name written inside it.
The information held on an entity is a set of characteristics that define the entity. These are known as attributes
The relationship between the entity, attributes and other entities are the relationships.

Degree of the relationship

1:1

One to One This is when something is directly linking to something else.

Example:

1:M

One to Many
When something is linking to multiple other things

Example

M:M

Many to Many
This is where any things link with many things

Example

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Examples