ERD Diagrams in Markdown

ERD (Entity-Relationship Diagram) is a tool that translates plain text descriptions of relational database schemas into graphical diagrams. It’s incredibly useful for documenting database schemas quickly and keeping them close to your code.

In MarkdownToPrettyPDF, you can create these diagrams using the erd language block.

Basic Syntax

Entities are defined just by stating their name. You can add attributes enclosed in curly braces {}, and you can define relationships with standard connector syntax.

syntax [Person] *name height weight +birth_location_id [Location] *id city state country Person *--1 Location

ERD

Advanced Syntax

You can use standard ER notation for cardinality:

• 1 : exactly one
• ? : zero or one
• * : zero or more
• + : one or more

syntax [Customer] *id name email [Order] *id customer_id order_date total_amount [OrderItem] *id order_id product_id quantity [Product] *id name price Customer 1--* Order Order 1--+ OrderItem Product 1--* OrderItem

ERD

Styling and Layout

The ERD tool automatically handles the layout, producing clean, structured diagrams representing your data model. Attributes marked with * are rendered as primary keys, while + denotes foreign keys.

Using the erd tool is an excellent way to maintain up-to-date and easily readable database schemas right within your documentation.