Gotcha, sorry for my misunderstanding. In that case, I defer to whatever Ken suggests.
Just to emphasize my understanding, though: I believe that Moodle will match people based on username (not email address). it sounds like there are already accounts for some of these students on the 3.6 site, since you mentioned that the email addresses might already be in use there.
Just to emphasize my understanding, though: I believe that Moodle will match people based on username (not email address). it sounds like there are already accounts for some of these students on the 3.6 site, since you mentioned that the email addresses might already be in use there.
I would guess that if the usernames from the 2.7 backup are changed to match the corresponding usernames for accounts in the 3.6 site, then the account on the 3.6 site will be enrolled in the course. I would not think that the different user ID numbers from the two sites would cause problems, because it would just make a simple match on the usernames, and then use the existing 3.6 account, forgetting everything else about the 2.7 account. I am assuming all of this by analogy with the "Upload users by CSV" feature, which matches on username, so I do not have definitive proof based on reading the code, just an educated guess. 😀