Seeking strategy/algorithm for maintaining order of records

I am building a site for my photography. The photographs are displayed by category. The category table has a field for "order" In my control panel I want to be able to change the order of the categories by changing the values in the category field. I can dynamically build a form of all categories and have a field for new order number, Then loop through the POST and update the values. The field is not unique, so I am not worried about DB errors. But I wonder if there is a better way. Thoughts please? Thank you Stephen