Hi Matt,
I'm in the same boat - trying to create a SQL query that shows each students' submission attempts, the date they were submitted, the date they were graded, and the time between them, but I've yet to get something that works. I have this query that gets each mod/assign submission, but I can't see how to tie this into the mdl_grade_grades_history table to get all grades for those submissions. How did you go?