I’ve been thinking a lot about invalid and zero temporal values and how to detect them with MySQL date and time functions because mk-table-checksum has to handle “everything” correctly and efficiently. The requirements are complex because we have to take into account what MySQL allows to be stored verses what it allows to be used in certain operations and functions, how it sorts a mix of real and invalid temporal values for MIN() and MAX(), how to detect a temporal value as equivalent to zero, and how different MySQL versions might affect any of the aforementioned.

At base, the four guiding requirements are: