The order of the rows in the absence of ORDER BY clause may be:
- different between any two storage engines;
- if you use the same storage engine, it might be different between any two versions of the same storage engine; Example here, scroll down to "Ordering of Rows".
- if the storage engine version is the same, but MySQL version is different, it might be different because of the query optimizer changes between those versions;
- if everything is the same, it could be different due to the moon phase and that is OK.