ER: Multiple Keys per Attribute
An attribute can carry several keys, comma-separated with or without a space (`PK, FK` / `PK,FK`), with or without a comment (#2115). Both spellings render as `PK,FK`.
er-multiple-keys-per-attribute.mmd
erDiagram
T {
string a PK, FK "c"
string b PK,FK
string d PK
string e FK
string f UK
string g PK, FK, UK
string h PK,FK,UK "with comment"
}