Re: Problem adding old database to MySQL Server 5.7

[Peter Brawley]

The best way to move databases from 5.6 to 5.7 is to back them up with mysqldump, then import those backups into 5.7.

Which is why it's usually recommended to run mysqldump on the existing server before installing 5.7. Uninstalling the previous MySQL version was an error.

Trying to import MySQL databases via file copy is fraught with issues that are likely to render the DBs unusable.

So if I'm faced with this problem, my first preference is to uninstall 5.7, copy the old MySQL folders to a safe place, re-install the old MySQL version, copy the old DB folders into the 5,6 installation, test them to see that everything is in order, then proceed as above.