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Attribute Keys

A `PK`/`FK`/`UK` key badge on a typed attribute — marking a primary, foreign, or unique key inline in the schema.

8 examples across every diagram type

Read more in the Mermaid docs →
ER diagram, Zombie Mermaid CUSTOMER PK int id string name UK string email date created_at
ER diagramER: Entity with Attributes
ER diagram, Zombie Mermaid ORDER PK int id FK int customer_id UK string invoice_number decimal total date order_date string status
ER diagramER: Attribute Keys (PK, FK, UK)
ER diagram, Zombie Mermaid CUSTOMER PK int id string name UK string email ORDER PK int id date created FK int customer_id PRODUCT PK int id string name float price LINE_ITEM PK int id FK int order_id FK int product_id int quantity places contains includes
ER diagramER: E-Commerce Schema
ER diagram, Zombie Mermaid USER PK int id UK string username UK string email date joined POST PK int id string title text content FK int author_id date published COMMENT PK int id text body FK int post_id FK int user_id date created TAG PK int id UK string name writes authors has tagged-with
ER diagramER: Blog Platform Schema
ER diagram, Zombie Mermaid STUDENT PK int id string name date dob string grade TEACHER PK int id string name string department COURSE PK int id string title FK int teacher_id int credits ENROLLMENT PK int id FK int student_id FK int course_id string semester float grade teaches enrolled has
ER diagramER: School Management Schema
ER diagram, Zombie Mermaid T c PK,FK string a PK,FK string b PK string d FK string e UK string f PK,FK,UK string g with comment PK,FK,UK string h
ER diagramER: Multiple Keys per Attribute
ER diagram, Zombie Mermaid CUSTOMER PK int id string name ORDER PK int id date due LINE_ITEM int qty places contains
ER diagramER: Style, classDef and Class
ER diagram, Zombie Mermaid CUSTOMER the primary key PK string name login address must be unique UK string email int age ORDER PK int id references CUSTOMER, deleted orders are archived rather than removed FK int customer_id places
ER diagramER: Attribute Comments