What happens if a "best reply" is deleted by its owner? Shouldn't we update the owning thread to nullify the
best_reply_id column? Otherwise, that column will refer to a reply that doesn't exist. In this episode, we'll add a database constraint to perform this update automatically. However, as we implement it, we'll encounter a few confusing issues that aren't so easy to debug.
View the source code for this episode on GitHub.