ER diagram

Entity-relationship diagrams describe a database schema: entities, their attributes, and the cardinality of the relationships between them. zombie-mermaid renders the full crow’s-foot notation along with PK/FK/UK key badges on typed attributes.

A schema's entities, and how they relate.

erDiagram
  CUSTOMER ||--o{ ORDER : places

Where ER diagrams come from, and how the syntax works.

Entity-relationship diagrams describe a database schema: the entities in a domain, the attributes each one carries, and the cardinality of the relationships that connect them. Mermaid’s syntax uses crow’s-foot notation to mark whether a relationship is one-to-one, one-to-many, or many-to-many, and a solid or dashed connecting line to distinguish identifying from non-identifying relationships. Attributes can declare a type, a name, and key markers — PK, FK, or UK — so a rendered diagram doubles as a readable schema reference, not just a shape.

Every ER diagram example, on its own page.

Explore the other diagram types.