MySql ordering

[Anon]

I have a MySQL database that I'm having customers upload item numbers to and display useing php. The item number can be an alphanumeric. Usually everything works fine but when the item number is 1000/01 I get a strange result. 1000/01 ends up after 1000/02.
my code:
query = SELECT * , date_format(DateIntro ,' %b %d %Y') as di from dedar_prdt ORDER BY 'ItemNum' ASC

my result:
Item #

1001/02
1001/03
1001/04
1001/05
1001/06
1001/07
1001/08
1001/01

I thought it might be dividing the number but I thought by puting '' around the variable would fix that.

Thanks

[Anon]

Figured it out, turns out my customer was putting in preceeding spaces in some records and MySQL is treating thoses as valid characters.