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Today, I would like to talk to you about the abbreviation of Emurr method, which may not be well understood by many people. In order to make you understand better, the editor has summarized the following contents for you. I hope you can gain something according to this article.

Emurr method is the abbreviation of entity-contact method (Entity-Relationship Approach).

It is an effective method to describe the conceptual model of real-world relations. Is a way to represent a conceptual relational model. The entity type is represented by "rectangular box", the entity name is written in the rectangular box, the attributes of the entity are represented by "elliptical frame" or rounded rectangle, and the "solid line segment" is used to connect it with the "entity" of the corresponding relationship.

The "diamond box" is used to indicate the cause of the relationship between the entity types, and the name of the connection is written in the diamond box, and the "solid line segment" is used to connect with the relevant entity type respectively. At the same time, the type of connection is marked on the side of the "solid line segment".

Composition elements:

The three basic elements of Emurr graph are entity type, attribute and relation, which are represented by:

1. Entity

It is generally believed that the thing that can be objectively distinguished from each other is the entity, which can be concrete people and things, or abstract concepts and relations. The key is that one entity can be distinguished from another, and entities with the same attributes have the same characteristics and properties. Abstract and depict similar entities with a collection of entity names and their attribute names. In the Emurr diagram, it is represented by a rectangle, and the entity name is written in the rectangle; for example, student Zhang San and student Li Si are entities. If it is a weak entity, set a solid rectangle outside the rectangle.

2. Attributes

An entity has a characteristic that can be described by several attributes. Attributes cannot be separated from entities, and attributes are relative to entities. In the Emurr diagram, it is represented by an oval, and undirected edges are used to connect it with the corresponding entity; for example, the student's name, student number, gender, are all attributes. If it is a multi-valued attribute, set a solid ellipse on the outside of the ellipse. If it is a derived attribute, it is represented by a dotted ellipse.

3. Contact

Connections, also known as relationships, reflect relationships within or between entities in the information world. The relationship within an entity usually refers to the relationship between the attributes that make up the entity; the relationship between entities usually refers to the relationship between different sets of entities. The Emurr diagram is represented by a diamond, and the contact name is written in the diamond box, which is connected with the relevant entity with an undirected edge, and the type of connection is marked on the undirected edge (1: 1, 1: n or m: n). For example, there is a teaching relationship between teachers and students, and there is a course selection relationship among students. If it is the connection of a weak entity, then put a diamond on the outside of the diamond.

After reading the above, do you have any further understanding of the abbreviation of Emurr method? If you want to know more knowledge or related content, please follow the industry information channel, thank you for your support.

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