How is the Emurr diagram formed in the database

I would like to share with you how the Emurr diagram in the database is composed. I believe most people don't know much about it, so share this article for your reference. I hope you will learn a lot after reading this article. Let's learn about it together.

Emurr diagrams, also known as entity-relationship diagrams, are used to show the relationships between entity sets. It provides a way to represent entity types, attributes, and relationships; a conceptual model used to describe the real world. The ER model is the design or blueprint of the database, which can be implemented as a database later.

In the Emurr diagram, an entity set is a similar set of entities (data objects in the data model) that can have attributes. In a database system, an entity is a table in a database or an attribute in a table, so the ER diagram shows the complete logical structure of the database by showing the relationship between the table and its attributes.

The composition of the Emurr diagram:

1. Entity (entity)

Entities represent data objects or components in the data model, for example, people, students, and music can all be used as a data object; in ER diagrams, they are represented by rectangles.

There is a special entity in the data model: the weak entity, which cannot be uniquely identified by its own attributes and depends on its relationship with other entities. In the ER diagram, weak entities are represented by double rectangles.

Note: each entity has its own entity members or entity objects, but these members or objects do not need to appear in the ER diagram.

2. Attribute (attribute)

Attributes represent the attributes of an entity, for example: a person's name, age, address, and other attributes; represented by an oval in the ER diagram, there are four types of attributes:

1), key attributes: can uniquely identify entities in the entity set

2), compound attributes: attributes that belong to other attribute combinations

As can be seen from the figure above: "student number" is a key attribute; "address" is a compound attribute, because "address" also consists of other attributes, such as province, city, district / county.

3), multi-valued attributes: attributes that can contain multiple values are called multi-valued attributes and are represented by double ellipses.

4), derived attribute: the value is dynamic and is derived from another property, represented by a dotted ellipse.

3. Relationship (relationship)

Relationships are used to represent relationships between entities, represented by diamonds in ER diagrams, and there are four types of relationships:

1), one on one

2), one-to-many

3), many to one

4), many to many

Example of Emurr illustration:

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