MyBB Community Forums

Basically, I'm trying to merge 2 MyBB forums together. When I merge them, I fear that some users will be merged together because of the fact that some accounts are the same names (there's 1k+ users). To solve this, I believe that a good solution would be to append a prefix of like old_ to all usernames of the old database so that there's no chance anything will go wrong. Any ideas on how to do this?

The following query may work

UPDATE mybb_users SET username=CONCAT("__old__", username)

Recommend having a back before you do it though.

I've never really used the merge system, but I'd recommend doing a trial run before you do it on a live setup.