anchor.diff:    PRIMARY KEY (`name`),
     UNIQUE KEY `name` (`name`),
     KEY `fk_study_users` (`username`)
  --- , CONSTRAINT `fk_study_users` FOREIGN KEY (`username`) REFERENCES `users` (`email`) ON DELETE CASCADE
   ) ENGINE=NDBCLUSTER DEFAULT CHARSET=latin1;
   /*!40101 SET character_set_client = @saved_cs_client */;
   
  
positive.code:   UNIQUE KEY `uid_UNIQUE` (`uid`),
    UNIQUE KEY `serial_UNIQUE` (`serial`),
    UNIQUE KEY `public_id_UNIQUE` (`public_id`)
  --,  CONSTRAINT `fk_yubikey_users` FOREIGN KEY (`uid`) REFERENCES `users` (`uid`) ON DELETE NO ACTION ON UPDATE CASCADE
  ) ENGINE=NDBCLUSTER  DEFAULT CHARSET=latin1;
  /*!40101 SET character_set_client = @saved_cs_client */;
  
  
negative.code:   UNIQUE KEY `id` (`id`),
    KEY `FK_jobhistory_user` (`user`),
    KEY `FK_jobhistory_study` (`study`)
  ) ENGINE=NDBCLUSTER DEFAULT CHARSET=latin1;
  /*!40101 SET character_set_client = @saved_cs_client */;
  
  