Crow's Foot vs Chen ERD Notation — Complete Comparison Guide

ER diagram notation comes in two main styles: crow's foot and Chen. They describe the same relationships — entities, attributes, and cardinalities — but look completely different and are used in different contexts. This guide explains what each notation looks like, when it is used, and how to read and draw both.

What Is Crow's Foot Notation?

Crow's foot notation represents entities as rectangles and shows relationships as lines between them. The ends of each relationship line carry symbols that indicate cardinality — how many instances of one entity can relate to the other.

Symbol at line end	Meaning	Reads as
||	Exactly one	"Exactly one"
o|	Zero or one	"Zero or one" (optional one)
}| or |{	One or more	"One or more" (required many)
}o or o{	Zero or more	"Zero or more" (optional many)

In Mermaid erDiagram syntax:

erDiagram
    CUSTOMER ||--o{ ORDERS : "places"
    %% One customer places zero or more orders

    ORDERS ||--|{ ORDER_ITEMS : "contains"
    %% One order contains one or more items

    EMPLOYEE ||--|| PROFILE : "has"
    %% One employee has exactly one profile

Crow's foot notation is the industry standard for professional database design. It is used in most commercial tools (dbdiagram.io, MySQL Workbench, DBeaver, DataGrip) and is what you will encounter in software development work environments.

What Is Chen Notation?

Chen notation (developed by Peter Chen in 1976) uses three shapes to represent a database schema:

Shape	What it represents	Example
Rectangle	Entity (table)	CUSTOMER, ORDER, PRODUCT
Oval	Attribute (column)	name, email, price
Diamond	Relationship between entities	"Places" (between CUSTOMER and ORDER)

In Chen notation, the cardinality is shown as numbers or letters at the ends of relationship lines:

• 1 on both ends: One-to-one relationship
• 1 on one end, N on the other: One-to-many
• M on one end, N on the other: Many-to-many

Chen notation visually separates attributes (ovals) from entities (rectangles), making the full attribute list visible in the diagram itself. This is more verbose than crow's foot but is considered more complete from a theoretical standpoint.

Chen notation is primarily taught in university database courses (particularly those using foundational DBMS textbooks like Ramez Elmasri's "Fundamentals of Database Systems"). It is rarely used in commercial software development.

Sell Custom Apparel — We Handle Printing & Free Shipping

Crow's Foot vs Chen — Side-by-Side Comparison

Feature	Crow's Foot	Chen Notation
Entity representation	Rectangle with columns listed inside	Rectangle (entity), oval (each attribute separately)
Relationship representation	Line between entities with symbols at ends	Diamond shape between entities
Cardinality	Shown via line-end symbols (||, o{, |{, o|)	Shown as 1, M, N labels on relationship lines
Attribute visibility	Columns listed in entity box	Each attribute shown as a separate oval connected to entity
Diagram size	Compact — all info in rectangular boxes	Large — ovals expand the visual footprint significantly
Readability for large schemas	Better — compact format scales	Worse — many ovals create visual clutter
Tool support	All professional tools	ERDPlus, Creately, some academic tools
Industry use	Standard in professional software development	Primarily in university teaching

Which Tools Support Each Notation?

Most modern online ERD tools use crow's foot notation exclusively:

Tool	Crow's Foot	Chen Notation	Free?
WildandFree ERD Maker	Yes	No	Yes — no signup
dbdiagram.io	Yes	No	Free account required
draw.io (diagrams.net)	Yes	Yes (manual shapes)	Yes — fully free
ERDPlus	Yes	Yes (native support)	Yes — fully free
Lucidchart	Yes	Limited	3 docs free
MySQL Workbench	Yes	No	Yes — desktop app
DBeaver	Yes	No	Yes — Community edition

If you need Chen notation: ERDPlus is the best free option with native Chen support. If you need crow's foot: any Mermaid-based tool, dbdiagram.io, or the WildandFree ERD maker all work.

Reading Crow's Foot Mermaid Notation

The Mermaid erDiagram notation encodes both ends of a relationship in one line. Here is how to read and write it:

%% Pattern: ENTITY_A [left-end][right-end] ENTITY_B : "label"
%% Left end = cardinality on ENTITY_A's side
%% Right end = cardinality on ENTITY_B's side

USERS ||--o{ ORDERS : "places"
%% Read as: One user places zero or more orders
%% || on left = exactly one user
%% o{ on right = zero or more orders

ORDERS ||--|{ ORDER_ITEMS : "contains"
%% Read as: One order contains one or more items
%% || = exactly one order
%% |{ = one or more items (required)

STUDENTS }o--o{ COURSES : "enrolls in"
%% Read as: Zero-or-more students enroll in zero-or-more courses
%% }o = zero or more students
%% o{ = zero or more courses (many-to-many)

The double dash (--) in the middle of the notation is always present and does not carry semantic meaning — it is just the line connector. The cardinality information is entirely in the characters before and after the dashes.

Frequently Asked Questions

What is the difference between crow's foot and Chen ER notation?

Crow's foot notation represents entities as rectangles with columns listed inside, and shows relationships as lines with special end symbols (crow's feet) indicating cardinality. Chen notation uses three shapes: rectangles for entities, ovals for each individual attribute, and diamonds for relationships. Chen is older and more verbose; crow's foot is the modern industry standard.

Which ER notation is used in industry?

Crow's foot notation is used almost universally in professional software development. Tools like MySQL Workbench, DBeaver, pgAdmin, DataGrip, and dbdiagram.io all use crow's foot. Chen notation is primarily taught in university database courses but is rarely seen in production database documentation.

Does the WildandFree ERD maker support Chen notation?

No. The free ERD maker uses Mermaid's erDiagram syntax, which implements crow's foot notation. For Chen notation (with diamond shapes for relationships and oval shapes for attributes), use ERDPlus — it is free, web-based, and supports Chen notation natively.

Can the same ER diagram be shown in both notations?

Yes — both notations describe the same underlying data model. A one-to-many relationship between CUSTOMER and ORDERS is expressed as a crow's foot symbol on the ORDER end in crow's foot notation, and as a 1:N label near a diamond-shaped PLACES entity in Chen notation. The semantic meaning is identical; the visual representation differs.