Mysql-clustered index and mysql-Index

Mysql-clustered index and mysql-Index
1. What is clustering index?

 

(Figure 1)

, You can see that the leaf node contains a complete data record. This index is called a clustered index.

2 clustering index features:

Because InnoDB data files need to be clustered by primary keys, InnoDB requires that the table have a primary key. If there is no primary key, InnoDB will replace it with a unique non-null index. Without such an index, InnoDB implicitly defines a primary key as a clustered index. This field is 6 bytes and its type is long integer. A table has only one clustered index.

The clustered index of InnoDB cannot be created separately. Generally, the primary key is used as the clustered index by default.