Explain

• explain <QUERY>;

Profile

• SELECT @@profiling;
  查看是否已经打开Profile
• SET profiling = 1;
  打开Profile
• <execute sql query>;
  执行SQL语句
• show profiles;
  查看做过Profile的SQL
• show profile for query <N>;
  打印对应SQL的Profile数据

参考资料

[1]. http://dev.mysql.com/doc/refman/5.6/en/explain-output.html
[2]. http://hi.baidu.com/gguoyu/item/4a588a0f41b9cb69d55a115f