Multiple instances of same foreign key in a single table I have a table that references the same foreign key multiple times (4 times) in the same table. Can someone explain why/how this makes sense?
Pedantically, A table doesn't reference a foreign key, it references a table via a foreign key.

It makes sense if it's necessary for the data model. 

Here's an example. A Sales Order is associated with multiple parties playing different roles, such as the Selling Party, Customer Party, Paying Party, and Order Taking Party.

create table sales_order (
  order_id int primary key,
  seller_party_id int not null references parties(party_id),
  customer_party_id int not null references parties(party_id),
  order_taken_by_party_id int not null references parties(party_id),
  payer_party_id int not null references parties(party_id),
  ...
);