mysql索引

添加唯一索引的三种方法

1、建表时

create table goods(
id int unsigned NOT NULL AUTO_INCREMENT,
.....
.....
.....
PRIMARY KEY (id),
UNIQUE KEY UK_domain(field_name)
)ENGINE=MyISAM DEFAULT CHARSET=utf8;

2、建表后

create unique index index_name on goods (field_name);

alter table goods add constraint index_name unique (field_name);