Author here. I didn't make it clear in the article but the table in question did have a primary key, which was migrated to an unique key, and then the new auto-incremental primary key was added.
As I mentioned in the article, the old ID field was then used in the update statement for the other tables.
I'm updating the article now to make that part clear.
As I mentioned in the article, the old ID field was then used in the update statement for the other tables.
I'm updating the article now to make that part clear.