MySql Ψһ¼ü

create table my_unique

(number char(10) unique comment'ѧºÅ :¿ÉÒÔΪnull',

name varchar(20), not null)charset utf8; ·½·¨1

¸´ºÏΨһ¼ü

create table my_unique2

(number char(10) not null comment'ѧºÅ',

name varchar(20) not null,

)charset utf8;

create table my_unique3

(id int primary key auto_increment,

number char(10) not_null,

name varchar(20) not null )charset utf8;

--×·¼ÓΨһ¼ü

alter table my_unique3 add unique key (number);

ɾ³ýΨһ¼üand ¸üÐÂ

alter table ±íÃû drop index Ë÷ÒýÃû×Ö;