Updating many records at a time

I have a situation where I am doing lots of complex sorting on records that already exist in a MySQL table. The table has a 'sort_order' field which means I can do a simple ORDER BY sort_order to keep it nice and quick on SELECT, it's only UPDATE which is slow. If I change the order that I want 10000 rows to be displayed, I am currently making 10000 SQL queries such as: UPDATE products SET sort_order=0 WHERE id='5'; UPDATE products SET sort_order=1 WHERE id='2'; UPDATE products SET sort_order=2 WHERE id='32'; and so on. Obviously I'd love to be able to put all of this into one query. Is there some way I can combine this with IN() ? UPDATE products set sort_order=**** WHERE id IN('5','2','32'); Many thanks in advance for any help / advice. Best wishes, Steve