ERD
Definition
ERD stands for entity relationship diagram. It is the standard data modeling tool used to design and communicate database schemas before or during software development.
ERD is the abbreviation engineers and architects reach for when they say 'let's draw the data model.' The full term is entity relationship diagram — see that entry for a detailed explanation of the three components (entities, attributes, relationships) and their history.
In practice, ERD refers to both the diagram type and the activity of drawing one. 'Let's ERD this' means 'let's model the data before we touch the schema.' The activity is a forcing function: you can't draw an ERD without making explicit decisions about what your system tracks and how records relate — decisions that otherwise get made implicitly and inconsistently.
Notation quick reference:
- Chen notation: rectangles for entities, ellipses for attributes, diamonds for relationships, '1' and 'N'/'M' for cardinality
- Crow's Foot notation: rectangles with attribute lists, line endings showing cardinality (single line = one, crow's foot = many, circle = zero/optional)
- UML class diagram notation: also used for data modeling, shows entities as classes with typed attributes
Most whiteboard ERDs use informal versions of Crow's Foot — boxes with column lists and lines between them. BoardSnap AI reads these and captures the entity names, key attributes, and relationship cardinalities as structured output.
Examples
- SaaS ERD: accounts table (1) → (many) users, (1) → (many) projects, (1) → (many) subscriptions
- Healthcare ERD: Patient (1) — has — (many) Appointment; Appointment (many) — attended by — (1) Doctor
- Marketplace ERD: Seller (1) — lists — (many) Listing (many) — bought via — (many) Transaction
- CMS ERD: Author (1) — writes — (many) Article; Article (many) — tagged with — (many) Tag
Snap a erd. Ship its actions.
BoardSnap turns any whiteboard — including this one — into a summary and action plan.