by Rick Jerz.
In my recent experimenting with a brand new Moodle 2.7 on an experimental server, I did not have success importing my moodle database into the 2.7 database. So I then installed Moodle 2.6.3, which matched my production moodle installation. Then, I was able to import my database. From that point, I then succeeded upgrading the experimental 2.6.3 to 2.7+.
I should also mention that my experimental server is using mySQL 5.6, whereas my production server is using mySQL 5.5.
So I am not sure if any of this helps anyone, I thought that I would just share some of my experiences.