Mermaid ER Diagram Design Tool

Quickly build entity-relationship models, clearly showing data entities, attributes and associations to help complete database structure design.

What is an ER diagram (entity-relationship diagram)

An Entity-Relationship diagram (or ER diagram) is a data modeling tool used to describe the relationships between data entities; it represents the data structure within a database using entities, attributes, and relationships.

Use cases

Database design

Show data structure through entities, attributes and relationships to help design a reasonable data storage model.

Business data analysis

Sort out the relationships between business data such as users, orders and products to understand core business logic.

Data model planning

Build a data model before system development, providing a design basis for database construction.

Database optimization

Analyze table structures and associations to discover data redundancy and optimize storage solutions.

System requirement communication

Help product, development and business teams communicate with a unified data perspective.

ER diagramFree templates

SaaS Multi-Tenant Schema

SaaS Multi-Tenant Schema

E-commerce Order Management ER Diagram

E-commerce Order Management ER Diagram

How to generate an ER diagram with Mermaid

1

Multiple editing methods

You can generate ER diagrams by writing Mermaid code, pasting Mermaid code, AI generation, image recognition, code summary and more. You can also draw ER diagrams using our built-in ER diagram templates.

2

Auto rendering

After entering Mermaid syntax, ER diagrams are generated and previewed in real time, with support for custom ER diagram styles and themes.

3

Export or share

You can download ER diagrams and save them locally. We support exporting ER diagrams to PNG, PDF, SVG, JPG, Markdown and other formats, or clicking the “Share” button to share the link with others.

4

Edit again

If you are not satisfied with the result, click the “Visual editing” button to edit the ER diagram again in the ProcessOn editor.

ER diagramCommon syntax

Syntax
Graphic
Meaning
erDiagram
ER diagram
Create an ER diagram
ENTITY { }
Rectangle
Define an entity
type field
Attribute marker
Define entity attributes
type field PK
Primary key
Define the entity primary key
type field FK
Foreign key
Define the entity foreign key
type field UK
Unique key
Define unique constraint fields
||
One
Exactly one
o|
Zero or one
Zero or one
|{
One or more
At least one
o{
Zero or one or more
Zero or more
ENTITY_A ||--|| ENTITY_B : label
One-to-one connection
Represents a one-to-one relationship between two entities
ENTITY_A ||--o{ ENTITY_B : label
One-to-many connection
Represents one entity corresponding to multiple entities
ENTITY_A }o--|| ENTITY_B : label
Many-to-one connection
Represents multiple entities corresponding to one entity
ENTITY_A }o--o{ ENTITY_B : label
Many-to-many connection
Represents a many-to-many relationship between two entities
ENTITY_A o|--|| ENTITY_B : label
Zero-to-one or one-to-one
Represents an optional one-to-one relationship
ENTITY_A o|--o{ ENTITY_B : label
Zero-or-many relationship
Represents an optional one-to-many relationship
: relationship
Line text
Add a descriptive name to an entity relationship
More Syntax

Why choose us

Online editing tool

Free templates

Powerful AI capabilities

Real-time preview

Export in multiple formats

Supports re-editing

ER diagramDrawing questions

What is an ER diagram (entity-relationship diagram)

A Mermaid ER diagram describes entities, attributes and the associations between entities in a database. It is an important tool for database design.

Can Mermaid ER diagrams be used for database design?

Yes. Mermaid ER diagrams help developers plan database table structures, field relationships and data models, improving database design efficiency.

What relationship types do Mermaid ER diagrams support?

Mermaid ER diagrams support one-to-one, one-to-many, many-to-many and other entity relationships, intuitively showing how data is connected.

How to create a Mermaid ER diagram?

After entering entity names, attributes and relationship definitions, the Mermaid editor will automatically generate the ER diagram and supports further adjustment and optimization.

Can Mermaid ER diagrams be exported?

Yes. Completed Mermaid ER diagrams can be exported to PNG, JPG, SVG, PDF, Markdown and other formats, making them convenient for technical documentation, proposal presentations and team collaboration.