MySQL SQL优化原理(order by group by distinct等)经典剖析

1.关于explain的详细介绍 参考：http://dev.mysql.com/doc/refman/5.1/zh/optimization.html

http:///tips/369/8263369.shtml    #explain    详解

2.order by和 group by内部原理参考简朝阳经典文章：

http:///database/mysql-performance-tuning-sql

http:///database/mysql_order_by_implement    #order by   详解

http:///database/mysql_group_by_implement    #group by   详解

http:///database/mysql_distinct_implement    #distinct   详解

http://dinglin.iteye.com/blog/1687358                   # like ‘%XXX%’使用覆盖索引优化