mysql有哪些索引类型

mysql> create table `student` (

    -> `id` int(10) not null auto_increment,

    -> `stuId` int(32) default null,

    -> `name` varchar(100) default null,

    -> primary key(`id`),

    -> unique key(`stuId`)

    -> ) engine=innodb auto_increment=1 default charset=utf8;

mysql> insert into student(stuId,name) values('123456789','jack');

Query OK, 1 row affected (0.10 sec)

mysql> insert into student(stuId,name) values('123456789','tom');

ERROR 1062 (23000): Duplicate entry '123456789' for key 'stuId'

mysql> insert into student(stuId,name) values(null,'tom');

Query OK, 1 row affected (0.11 sec)