post order by custom field in wp_post

I’d added a new field in wp_posts table let say ‘abc’ now I want list the post according to ‘abc’ can anybody help me with that.

Another thing I want to do this by plugin, i’d tried query_posts($query_string .’&orderby=abc&order=asc&posts_per_page=-1′);
which doesnt seem to work for custom fields. I think what I want to do can be done through get_post() but I’m clueless how.

All help will be highly appreciated.

Thanks in advance,
Adi