Entity relationship

erDiagram
    CUSTOMER ||--o{ ORDER : places
    ORDER ||--|{ LINE-ITEM : contains
    CUSTOMER }|..|{ DELIVERY-ADDRESS : uses
    CUSTOMER {
        string name
        string email
    }
    ORDER {
        int id
        date placed
    }

Syntax

• A ||--o{ B : label relates two entities; each end's pair of marks is its cardinality — |o zero or one, || exactly one, }o zero or more, }| one or more.
• -- is an identifying relationship, .. a non-identifying one.
• ENTITY { type name } lists attributes; PK, FK and UK after one mark keys, and a quoted string comments it.