Analytics and reporting

Hi,

I created a query to get the answers for each question from the highest scored attempt for each student:

select u.username, question.name, case when qas.state = "gradedright" or qas.fraction = qatt.maxmark then 1 else 0 end correct
	FROM mdl_quiz AS q
		JOIN mdl_course_modules AS cm ON cm.instance = q.id
		JOIN mdl_quiz_attempts qa ON q.id = qa.quiz
			and qa.id = (
				select id
				from mdl_quiz_attempts
				where quiz = q.id
					and userid = u.id
				ORDER BY sumgrades DESC
				LIMIT 1
			)
		JOIN mdl_user AS u ON u.id = qa.userid
		JOIN mdl_question_usages AS qu ON qu.id = qa.uniqueid
		JOIN mdl_question_attempts AS qatt ON qatt.questionusageid = qu.id
		JOIN mdl_question AS question ON question.id = qatt.questionid
		JOIN mdl_question_attempt_steps AS qas ON qas.questionattemptid = qatt.id
			and qas.id = (
			    SELECT sortqas.id
			    FROM mdl_question_attempt_steps sortqas
			    WHERE sortqas.questionattemptid = qatt.id
				ORDER BY sortqas.timecreated DESC
				LIMIT 1
		    )
	    JOIN mdl_course crs on crs.id = cm.course
	WHERE cm.id = ?

However, it seems some of the correct answers are registered with mdl_question_attempt_steps.state = "completed" instead of "gradedright", so I considered mdl_question_attempt_steps.fraction = mdl_question_attempts.fraction as correct answers as well.

Can someone please tell me if this is a consistent consideration or if it has any issues like precision differences or whatever? Also, is there a better way to determine correct answers?

Thanks!