What is the principle of B-tree indexing in MySQL?

B-tree index is a commonly used database index structure that speeds up data retrieval by organizing data in a specific way.

1. A B-tree is a balanced multi-way search tree, where each node can store multiple keys and pointers, reducing the height of the tree and speeding up searches.
2. A B-tree index will sort data based on the values of a specific column and create a B-tree structure. Each node contains multiple values and pointers pointing to the next level of nodes.
3. When searching for a value, the database will first search in the B-tree index, using the value and pointers of the nodes to quickly locate the page where the target data is located.
4. B-tree indexes not only improve search speed but also support operations like range queries and sorting because B-trees are ordered.

In general, B-tree index speeds up database query performance by creating a balanced multi-way search tree structure that quickly locates the target data.