ER diagram
An entity-relationship (ER) diagram is a data-modeling diagram that shows entities (database tables or objects), their attributes, and the relationships between them.
In depth
ER diagrams are the foundational tool for designing relational databases. Entities are usually rendered as rectangles containing attributes; relationships connect entities with cardinality markers (1:1, 1:N, N:M). The classic notation is Chen's; modern tools use crow's-foot notation almost universally.
Beyond databases, ER diagrams help document any domain model — a CRM's account/contact/opportunity hierarchy, an e-commerce catalog's product/variant/inventory model, or a content platform's post/author/comment graph.
OpenCharts supports ERD-style nodes with attached attribute tables and crow's-foot relationship markers. AI generation can produce a draft ERD from a description of the domain.
Examples
- E-commerce product catalog
- CRM data model
- Booking system entities
Also known as
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Build an ER diagramRelated terms
UML
UML (Unified Modeling Language) is a standardized family of diagrams used in software engineering to model systems, including class, sequence, activity, state, and use-case diagrams.
Data flow diagram
A data flow diagram (DFD) is a graphical representation of how data moves through a system, showing data sources, processes, data stores, and external entities.
System context diagram
A system context diagram is a high-level architecture diagram that shows a system as a single box at the center, surrounded by the people and external systems it interacts with.