er-attribute-keys-pk-fk-uk.mmd
erDiagram
ORDER {
int id PK
int customer_id FK
string invoice_number UK
decimal total
date order_date
string status
}All three key constraint types rendered as badges.
erDiagram
ORDER {
int id PK
int customer_id FK
string invoice_number UK
decimal total
date order_date
string status
}