Assignment

I posted this in the database forum 25 days ago but haven't had a response so thought I'd try here... I'm running 1.9.5+ and I am writing an SQL report to track and profile how long it takes instructors to grade submitted assignments. I'm reporting off the mdl_assignment_submissions table and I've discovered the following:

1) There is a bug in the code that (in many cases) prevents the timecreated column from being populated in the mdl_assignment_submissions table.

2) The few cases where timecreated is populated, the timemodified column is always populated with the same value as timecreated. However, there are a significant number of rows where timemodified has a value and timecreated does not.

3) If the timemarked column is non-zero (meaning the assignment has been graded) then in almost all cases, timemodified is populated with a value which is different from timemarked.

4) If timemarked is zero (not graded) there is NEVER a value in timecreated or timemodified, There is no way to tell how long an assignment has been waiting to be graded.

Is there some way I can really find out when the assignment was submitted? It is turning out to be a real pain that timecreated in the mdl_assignment_submissions table is not populated.

I was able to take a few entries from the mdl_assignment_submissions table and match up some entries from the mdl_log table. I used userid, course, module and action to find corresponding activity between the two tables. This does not seem to be a 100% match every time so I don't think this is a good solution for estimating the time of sub.

I've even considered adding a trigger to the database so that any time a row is inserted into the mdl_assignment_submissions table a trigger populates the timecreated column.

Is there any other way the backtrack and get the timecreated for all these 100,000 records that don't have a value?