Supported Dialects¶

Compare the three supported ERD output formats.

Mermaid.js¶

Best for: GitHub READMEs, web documentation, quick sharing

Pros¶

Native GitHub support
No external tools needed
Easy to edit in markdown
Live preview in browsers

Cons¶

Limited styling options
Simpler diagram syntax

Example¶

erDiagram
    Customer {
        varchar first_name
        varchar last_name
        varchar email
    }
    Order {
        ForeignKey customer
        datetime order_date
    }
    Customer ||--o{ Order : places

Usage¶

python manage.py generate_erd -d mermaid -o erd.md

PlantUML¶

Best for: Enterprise documentation, detailed diagrams, printing

Pros¶

Highly customizable
Professional output
Many export formats (PNG, SVG, PDF)
Rich relationship notation

Cons¶

Requires PlantUML server or local installation
Steeper learning curve

Example¶

@startuml
entity Customer {
    * id : bigint
    --
    varchar first_name
    varchar last_name
    varchar email
}
entity Order {
    * id : bigint
    --
    ForeignKey customer
    datetime order_date
}
Customer ||--o{ Order : places
@enduml

Usage¶

python manage.py generate_erd -d plantuml -o erd.puml

dbdiagram.io¶

Best for: Database design, collaboration, SQL generation

Pros¶

Interactive web editor
SQL export capability
Team collaboration
Database schema validation

Cons¶

Requires internet connection for web tool
Proprietary platform

Example¶

Table Customer {
  id bigint [pk]
  first_name varchar
  last_name varchar
  email varchar [unique]
}

Table Order {
  id bigint [pk]
  customer bigint [ref: > Customer.id]
  order_date datetime
}

Ref: Order.customer > Customer.id

Usage¶

python manage.py generate_erd -d dbdiagram -o erd.txt

Comparison Table¶

Feature	Mermaid.js	PlantUML	dbdiagram.io
GitHub Support	✅ Native	❌ Image only	❌ Image only
Customization	Limited	High	Medium
Export Formats	SVG/PNG	PNG/SVG/PDF	PNG/SQL
Learning Curve	Low	Medium	Low
Offline Use	✅ Yes	✅ Yes	❌ No
Team Collaboration	❌ No	❌ No	✅ Yes
SQL Generation	❌ No	❌ No	✅ Yes

Recommendation¶

Use Mermaid.js for GitHub projects and README files
Use PlantUML for enterprise documentation and printing
Use dbdiagram.io for database design and team collaboration