In my module, I can call drupal_flush_all_caches(), and this would clear the cache for all the nodes.

Is there a way to clear the cache for a single node?

What I need to do is setting up a module that, when it selects a story on a list, it changes the value of a node field. Right now, I change the field value by updating the database table containing that value, but I need to clear the cache for the value to be updated across the site.

Is there's a better way to update a node than directly changing the database table?