look at http://www.xaprb.com/blog/2006/07/04/how-to-exploit-mysql-index-optimizations/
prior to MySQL 5.5, MYISAM is default engine. InnoDB becomes default from 5.5.
difference between InnoDB and MYISAM,布布扣,bubuko.com
difference between InnoDB and MYISAM
原文：http://www.cnblogs.com/litao9046/p/3748233.html