What is the relational database index, the purpose, the principle and the b,b+-tree difference

What exactly is a database index and how does it work? -CSDN Blog
http://blog.csdn.net/weiliangliang111/article/details/51333169
MySQL indexing principle and slow query optimization-
Https://tech.meituan.com/mysql-index.html
How the database index is implemented-CSDN blog
http://blog.csdn.net/kennyrose/article/details/7532032

Difference:

, the difference has the following two points:

1. B + Tree only the leaf node will have a pointer to the record (ROWID), while the second tree has all the nodes, the index entries appearing on the internal node no longer appear in the leaf node.

2. All the leaf nodes in the B + tree are connected by pointers, while the B. Tree does not.

Advantages of B + trees:

1. Non-leaf nodes do not take rowid, so that a block can hold more index entries, one can reduce the height of the tree. The second is that an internal node can locate more leaf nodes.

2. The leaf nodes are connected by pointers, the range scan will be very simple, and for the B-tree, it is necessary to move around the leaf node and the internal node continuously.

Advantages of B-Tree:

For the internal node of the data can be directly obtained, do not have to be based on the leaf node to locate.

Talk about R-Trees-csdn Blog-from B-trees, + + trees, and b* trees
http://blog.csdn.net/v_JULY_v/article/details/6530142

The difference between B-and + + trees-ivictor-Blog Park
Http://www.cnblogs.com/ivictor/p/5849061.html

What is the relational database index, the purpose, the principle and the b,b+-tree difference