http://blog.csdn.net/zhxp_870516/article/details/8434539
http://www.jb51.net/article/49346.htm
https://jingyan.baidu.com/article/27fa7326b574e746f8271fb3.html
SHOW INDEX
https://www.cs.usfca.edu/~galles/visualization/BST.html 这个是可以看到mysql数据增加的过程的在线地址 ！
