Clustered index (clustered index), nonclustered index (nonclustered index)

Clustered index （ Cluster index ）：1、 The order of indexes is consistent with the physical order of records . 2、 Leaf nodes are data nodes  

Nonclustered indexes （ Nonclustered index ）：1、 The order of the indexes is inconsistent with the physical order of the records . 2、 Leaf nodes are pointer nodes .

Clustered index （ Cluster index ） And nonclustered indexes （ Nonclustered index ） All are B+ Trees .

MyISAM The default is nonclustered index , There are two files , Data files and index files

InnoDB The default is clustered index , A file data file is an index file .

InnoDB The engine primary key index is a clustered index

InnoDB Primary key index of , Directly query data , The auxiliary index first looks up the keyword , Checking data .

InnoDB Engine its secondary index , Its leaf node stores the value of the primary key

The link to the reference article is as follows ：

https://blog.csdn.net/qq_37189082/article/details/99246581

https://blog.csdn.net/qq_43193797/article/details/88593304

https://www.jianshu.com/p/d95d6d692e2c

How to create clustered and nonclustered indexes

https://zhidao.baidu.com/question/918836349194987379.html

Additional interview questions

https://www.jianshu.com/p/1990261fca3f