MySQL给字段唯一索引的三种方法

DROP TABLE IF EXISTS `student`;
CREATE TABLE `student` (
  `stu_id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(255) DEFAULT NULL,
  PRIMARY KEY (`stu_id`),
  UNIQUE KEY `UK_student_name` (`name`) 
) ENGINE=InnoDB AUTO_INCREMENT=12 DEFAULT CHARSET=utf8;

create unique index UK_student_name on student (name);

alter table student add constraint uk_student_name unique (name);