Difference between MySQL 5.6 and 5.7

Changes between MySQL 5.6 and 5.7

As usual with new MySQL versions, many new features have been added and some existing behaviors have been altered. This may cause potential issues with your setup if you neglect the importance of research and testing - new behavior may not be compatible with your application.
One of the main changes is the way that internal metrics are made available. In MySQL 5.6, you could query information_schema.global_status table and get some data about MySQL internals. In MySQL 5.7, this data is available through the performance_schema - such change may render your monitoring and trending software useless unless you enable ‘compatibility’ mode.
Some changes have been introduced in the default SQL mode - right now MySQL uses STRICT_TRANS_TABLES by default. This is great change but it sure can break compatibility with older applications.

Another important change is related to the authentication mechanism. Pre-4.1 passwords (‘old passwords’) have been removed, a new authentication system has been added. Amongst others, password expiration policy has been introduced - this can become a serious issue as the default settings may not be safe for systems upgraded from older MySQL versions - it’s better to set policies manually instead of relying on defaults, which may change in the future.

Those are definitely not the only changes which may pose a problem in an upgrade process. We’ve covered these in more detail in our database upgrade guide, “Migrating to MySQL 5.7”.