I have a couple of posts that are getting hammered by bots so I want to change the permalink slugs. However, when I do so WP redirects from the old to the new slug. I want the old slug to give a 404. I've managed to find a partial answer in another thread:
"delete the _wp_old_slug post meta entry from the database for that post"
... but I'm having trouble finding _wp_old_slug in phpMyAdmin - I admit I'm no expert with this, so detailed instructions would be very welcome.
UPDATE: I have now discovered the 'Remove Old Slugs' plugin which resolves my problem, but I would still like to know where to look in phpMyAdmin, for my own knowledge.