Merge deleted users with existing user

[Blacky63 0]

We have a couple of deleted users which created a new account and we want to merge their old post with their new account.

The old names are like "Guest John" and new account is John.

Now with Xenforo this seems rather easy because the deleted user gets a seperate number like "deleted user xxx" where xxx is (if I'm correct) the deleted user number, for example 65 foro 65th deleted user.

Ofcourse the Guest John gets user_id 0 which all guest users have. So I found a thread on Xenforo how to first replace the old username (guest John) with John and afterwards change refer the post id's of the deleted user to the existing user. I'm not sure if I'm allowed to link to there, so I will post the commands.
Like this:

UPDATE `xf_post` 	SET `username` = replace(username, 'Deleted member 16', 'Horace')