mysql Multiple Foreign Keys in a Table to the Same Primary Key

Question

I have a table user with userID as the primary key. I have another table called Friends. In the Friends table, I have two

Answer 1

No, you should create two foreign keys:

ADD CONSTRAINT `ufd_users_fk` FOREIGN KEY (`userId`) 
  REFERENCES `users` (`userId`) 
  ON DELETE CASCADE ON UPDATE CASCADE,
ADD CONSTRAINT `ufd_users_fk` FOREIGN KEY (`friendId`) 
  REFERENCES `users` (`userId`) 
  ON DELETE CASCADE ON UPDATE CASCADE;