What columns stores the slug in wordpress

At the risk of heresy, I am going to say it is not completely true. I was updating some slugs and found the post_name field does not change. On further searching, I found the wp_postmeta table has an entry under meta_key name 'custom_permalink' that has the latest slug path.

The slug for Posts and Pages are stored in the wp_posts posts table in the column post_name. Just be aware that all the automatic saves as well as attachments are stored in the same table, so there will not be a solid column full of slugs, but only one for each "parent" (parent to the revisions) Post or Page.