4、Mysql主键索引创建的实例

1、在上面了解了Mysql常见的索引后,这里进行Mysql索引实例的创建.

2、主键索引

2.1 在创建表的时候,指定主键索引

create table table_primarykey
(   id int primary key auto_increment  ,
name varchar(20)
);

利用 show create table table_primarykey ; 来查看表的创建语句

+------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------+

| Table | Create Table |

+------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------+

| table_primarykey | CREATE TABLE `table_primarykey` (

`id` int(11) NOT NULL DEFAULT '0',

`name` varchar(20) DEFAULT NULL,

PRIMARY KEY (`id`)

) ENGINE=InnoDB DEFAULT CHARSET=utf8 |

+------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------+

2.2先创建表,在增加主键索引

create table table_primarykey
(   id int  auto_increment  ,
name varchar(20)
);

alter table table_primarykey
add primary key (id);

利用 show create table table_primarykey ; 来查看表的创建语句

+------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------+

| Table | Create Table |

+------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------+

| table_primarykey | CREATE TABLE `table_primarykey` (

`id` int(11) NOT NULL DEFAULT '0',

`name` varchar(20) DEFAULT NULL,

PRIMARY KEY (`id`)

) ENGINE=InnoDB DEFAULT CHARSET=utf8 |

+------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------+

3、查看表上的索引

show indexes from table_primarykey;

执行的结果如下:

+------------------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+

| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |

+------------------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+

| table_primarykey | 0 | PRIMARY | 1 | id | A | 0 | NULL | NULL | | BTREE | | |

+------------------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+