mysql Beberapa Kunci Asing dalam Tabel ke Kunci Utama yang Sama

Tidak, Anda harus membuat dua kunci asing:

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;