First, and foremost, if you are not using InnoDB, close this question, rebuild with InnoDB, then see if you need to re-open the question. MyISAM is not preferred and should not be discussed. How did you build the indexes in MySQL? There are several ways to explicitly or implicitly build indexes; they lead to better … Read more
https://web.archive.org/web/20161221112438/http://www.toadworld.com/platforms/oracle/w/wiki/11001.oracle-b-tree-index-from-the-concept-to-internals Notes: Databases do not directly implement indexes based on B-tree but on a variant called B+ tree. Which according to wikipedia: A B+ tree can be viewed as a B-tree in which each node contains only keys (not key-value pairs), and to which an additional level is added at the bottom with linked leaves. … Read more