So this works...
ALTER TABLE variation AUTO_INCREMENT = 10;
But I want to do this;
ALTER TABLE variation AUTO_INCREMENT = (
I don't know if this is a good idea, but could you do it with 2 queries in a server side language, for example, PHP?
$incrementStep = Db::query('SELECT MAX(id)+1 FROM old_db.varaition');
Db::query('ALTER TABLE variation AUTO_INCREMENT = ' . (int) $incrementStep);
Assuming that Db::query is a magic query method that returns exactly what you want, every time :)