auto_increment without primary key in innodb?

[Yang Zhang]

In innodb, is it possible to have an auto_increment field without
making it a (part of a) primary key? Why is this a requirement? I'm
getting the following error. Thanks in advance.

ERROR 1075 (42000): Incorrect table definition; there can be only one
auto column and it must be defined as a key
-- 
Yang Zhang
http://www.mit.edu/~y_z/