3 способа удалить данные из таблицы, которых нет в другой таблице

mysql delete
1. LEFT JOIN/IS NULL
DELETE b FROM tbl
  LEFT JOIN rel ON rel.id = tbl.fileid 
      WHERE rel.id IS NULL
2. NOT EXISTS
DELETE FROM tbl 
 WHERE NOT EXISTS(SELECT NULL
                    FROM rel
                   WHERE rel.id = tbl.fileid)
3. NOT IN
DELETE FROM tbl
 WHERE tbl.fileid NOT IN (SELECT rel.id 
                        FROM rel)