--source include/have_innodb.inc

CREATE TABLE `t1` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `b` int(11) DEFAULT NULL,
  `c` int(11) DEFAULT NULL,
  `orderby` int(11) DEFAULT NULL,
  PRIMARY KEY (`id`),
  KEY `orderby` (`orderby`)
) ENGINE=MyISAM ;

insert into t1 (b,c,orderby) values (rand()*100, rand()*100, rand()*200);

insert into t1 (b,c,orderby) select rand()*100, rand()*100, rand()*200 from t1;
insert into t1 (b,c,orderby) select rand()*100, rand()*100, rand()*200 from t1;
insert into t1 (b,c,orderby) select rand()*100, rand()*100, rand()*200 from t1;
insert into t1 (b,c,orderby) select rand()*100, rand()*100, rand()*200 from t1; 

insert into t1 (b,c,orderby) values(1,1,1);
insert into t1 (b,c,orderby) values(2,1,1);
insert into t1 (b,c,orderby) values(3,1,2);
insert into t1 (b,c,orderby) values(4,1,2);

--vertical_results
explain extended select * from t1 order by orderby;
explain extended select * from t1 order by id;

alter table t1 engine=innodb;

explain extended select * from t1 order by orderby;
explain extended select * from t1 order by id;