When you do a SELECT * in MySQL query from MATLAB, you would expect all the entries in the table to be returned.
Apparently, there are cases where it will not return everything. (Matlab R2013a, MySQL 5.5.32)
It seems that if you have '0000-00-00 00:00:00' in the datetime field of a row, which is the zero value of the datetime type, the row will not be returned even if you do the select all query.
However, if you are querying other columns (besides the datatime column), the row that has the zero value datetime will be returned.