contact list re-ordering (php/mySQL CMS design)

Dear guru's, Hit a problem while developing a CMS with php/mySQL. Part of this is a contact list and this works ok (add/edit/delete with insert/update/delete queries). Now the client has requested a new feature: ability to change the order in which the contacts are being presented in the public part of this CMS (don't ask me why). I've added a field 'show_pos' to the contacts table and am able to change its value when I edit an existing record or add a new one. What I can't wrap my head around at the moment is how one deals with updating 'show_pos' for the OTHER records (while editing/deleting present record (WHERE id='$id')? Could anyone give me some pointers as to how this could be done in php and/or SQL (preferable). I sure hope anyone understands what I mean ... Cheers! newbie@a_loss