We start using moodle 2.3.1 on a new install (not upgrading) with Oracle 10.2 database.
We found a error in SQL statements in assignments módules.
After creating a assignment, when teacher click in the link to see the works sent by students the application display a error about the SQL statement (with params replaced):
Looking at sentence we found that there are two columns renamed with the "AS" keyword that will have the same name of the other columns not renamed: firstname, lastname.
Solution (for now):
We replaced the alias for the columns with "firstnamex" and "lastnamex" offline with offlinex in the file <moodlehome>/mod/assign/gradingtable.php: