The difference between MySQL clustered index and non clustered index

mysql The difference between clustered index and non clustered index

mysql Clustering Indexes He Fei Clustering Indexes Is the difference between the ： about Clustering Indexes , Table data is stored in sequence , That is, the index order is consistent with the physical storage order of table records ; For nonclustered indexes , The order in which table data is stored is independent of the order of the indexes .

 

 

mysql Introduction to the differences between clustered index and non clustered index ：

Cluster index ：

Table data is stored in sequence , That is, the index order is consistent with the physical storage order of table records .

Cluster index Leaf nodes store data rows and B-Tree Indexes .

There can only be one clustered index in a table , Because there can only be one real physical storage order .

Clustered indexes are sparse indexes , The primary index storage on the data page is the page pointer , Non row pointer .

Nonclustered index ：

The order in which table data is stored is independent of the order of the indexes .

For nonclustered indexes , The leaf node contains the row primary key value and the primary key value as the “ The pointer ”, Find through secondary index , two B-Tree lookup InnoDB Adaptive hash indexing can reduce such repetitive work .

Non clustered indexes are dense indexes , On the upper index page of the data page, it stores a record for each data row .