mysql資料庫中的KEY和PRIMARY KEY的疑惑?

??灏辯?存??o???懼??浠ｇ??

涔???????杩?绡???绔?

#
alter table testMyIndex add (hometown VARCHAR(45) KEY,money FLOAT UNIQUE); #姝ｇ‘

#?ラ??浜?锛?Multiple primary key defined ??绀哄凡缁???primary key(涓婚??)浜?
#alter table testMyIndex add (remarks VARCHAR(50) KEY,bankNumber VARCHAR(16) UNIQUE);
           

?ラ??淇℃??[Err] 1068 - Multiple primary key defined

??璁闆?key?抽??瀛???浠ョ?ㄦ?ュ０??????绱㈠?,??涔?姝ゆ??ey?抽??瀛?????primary key??浣??ㄤ??

??????寤鴻〃??璇??ユ?瘋??烘??

#?ョ????寤鴻〃??璇???SHOW CREATE TABLE testMyIndex;

#??????寤鴻〃??璇??ユ?瘋??烘??CREATE TABLE `testmyindex` (
  `xing` varchar(30) DEFAULT NULL,
  `ming` varchar(20) DEFAULT NULL,
  `email` varchar(30) DEFAULT NULL,
  `workCity` varchar(30) DEFAULT NULL,
  `schoolName` varchar(40) DEFAULT NULL,
  `hometown` varchar(45) NOT NULL,
  `money` float DEFAULT NULL,
  PRIMARY KEY (`hometown`),
  UNIQUE KEY `index_email` (`email`),
  UNIQUE KEY `index_workCity2` (`workCity`),
  UNIQUE KEY `index_schoolName_workCity2` (`schoolName`,`workCity`),
  UNIQUE KEY `index_schoolName2` (`schoolName`),
  UNIQUE KEY `money` (`money`),
  KEY `xm` (`xing`,`ming`),
  KEY `index_workCity` (`workCity`),
  KEY `index_schoolName_workCity` (`schoolName`,`workCity`),
  KEY `index_schoolName` (`schoolName`)
) ENGINE=InnoDB DEFAULT CHARSET=gb2312
           

?