Mysql索引

https://www.kancloud.cn/thinkphp/mysql-design-optimalize/39320

http://www.cnblogs.com/hustcat/archive/2009/10/28/1591648.html

先记录下好的博客吧

二叉树：http://www.cs.carleton.edu/faculty/jgoldfea/cs201/spring11/inclass/Tree/BTreefinalNew.pdf