title: Foreign key constraint is incorrectly formed?
body: <p>I got this errore when create table: Foreign key constraint is incorrectly formed???</p>
  
  <pre><code>{create table comment(
  Comment_ID int UNSIGNED AUTO_INCREMENT not null,
  User_1 varchar(50) not null,
  Note_ID int(11) UNSIGNED not null,
  PRIMARY key(Comment_ID),
    CONSTRAINT `fk_1` FOREIGN KEY (`User_1`) REFERENCES `user` (`Dev_ID`),
    CONSTRAINT `fk_2` FOREIGN KEY (`User_2`) REFERENCES `user` (`Dev_ID`),
    CONSTRAINT `fk_3` FOREIGN KEY (`Note_ID`) REFERENCES `note`(`Note_ID`)
  )ENGINE=InnoDB DEFAULT CHARSET=utf8;
  }
  </code></pre>
  
  <p>it's ok when i remove fk_3<br>
  this my note table</p>
  
  <pre><code>{ 
  CREATE TABLE `note` (
   `Dev_ID` varchar(50) NOT NULL,
    `Note_ID` int(11) UNSIGNED NOT NULL,
    `Title` varchar(200) NOT NULL,
    `Time` datetime NOT NULL,
    `Mood` int(11) NOT NULL,
    `Body` varchar(3000) NOT NULL,
    `Visible` tinyint(1) NOT NULL DEFAULT '1',
    `Share` tinyint(1) NOT NULL DEFAULT '0',
    `Update` tinyint(1) NOT NULL DEFAULT '0',
    PRIMARY KEY (`Dev_ID`,`Note_ID`),
    CONSTRAINT `fk_note_user` FOREIGN KEY (`Dev_ID`) REFERENCES `user` (`Dev_ID`) ON UPDATE CASCADE
  ) ENGINE=InnoDB DEFAULT CHARSET=utf8
  }
  </code></pre>
  
  <p>Thanks for help!</p>