What is an EER diagram? ER diagram vs EER diagram

EER diagram (Enhanced Entity The Enhanced Entity Relationship Diagram (ERD), also known as the Enhanced Entity Relationship Diagram, is a powerful tool for visual database design. It not only inherits the essence of the traditional ER diagram (Entity Relationship Diagram), but also expands more functions and details, making database design more intuitive and flexible. The following will explain the EER diagram in detail from the aspects of concepts, differences from ER diagrams, symbols, drawing tutorials, examples, etc.

Ⅰ. EER Diagram Concept

EER diagram is a graphical database design tool that uses graphical symbols and connecting lines to represent entities, attributes, and the relationships between them. Entities represent tables in the database, attributes represent fields in the table, and relationships represent the connections between different tables. EER diagrams are not only used to show the structure of the database, but also help developers better plan and manage the database to meet the needs of the application.

School Management System EER Diagram

Ⅱ. EER diagram application scenarios

EER diagrams play an important role in a variety of database design and management scenarios. It is commonly used for:

Database design: Developers can use EER diagrams to design the database structure, including defining tables, fields, and relationships between them.

Database optimization: Through EER diagrams, developers can visually see the redundancy and complexity in the database and optimize it.

Database documentation: The EER diagram can be used as a document of the database structure to facilitate understanding and communication between developers and database administrators.

Database reverse engineering: EER diagrams can also be used to generate SQL scripts for databases to quickly create databases.

Ⅲ. The difference between EER diagram and ER diagram

ER diagram is an entity relationship diagram, and EER diagram is an extension of ER diagram. There are significant differences in functions and details between the two:

Functional extension: EER diagram provides more functions and details, such as subclass/superclass, multiple relationships, multi-valued dependencies, etc., making database design more flexible and extensible.

Rich symbols: EER diagrams use more symbols and concepts to better describe data models in the real world.

Wide range of application scenarios: EER diagrams are not only used for database design, but also for database optimization, documentation, reverse engineering and other scenarios.

If you want to know more about ER diagrams, you can check What is an Entity Relationship Diagram (ERD) and How to Draw an ERD？ .

IV. Symbols of EER Diagram

1. Entity

Representation method: Represented by a rectangular frame.

Definition: An entity is an independent, specific thing or object in the real world, which usually corresponds to a table in the database.

Function: Entity is the basic unit of database design and is used to describe objects in the real world.

2. Attribute

Representation method: Represent it with an elliptical frame and connect it with the corresponding entity with an undirected line.

Definition: An attribute is a characteristic or description of an entity that describes a specific feature or aspect of the entity.

Function: Attributes usually correspond to fields in a table in a database and are used to store specific information about an entity.

3. Relationship

Representation method: Represented by a diamond frame and connected to the relevant entities with undirected lines.

Definition: Relationships represent connections and dependencies between entities.

type:

One-to-one (1:1): There is a unique correspondence between one entity and another entity.

One-to-many (1:n): There is an association between one entity and multiple entities.

Many-to-many (m:n): Multiple entities can be related to each other.