Change group-by. I know what was there was equivalent, but Postgres is pedantic about...

diff --git a/mod/quiz/report/reportlib.php b/mod/quiz/report/reportlib.php
index a65353ea9cdb74c4a0785350aacfdff35e2b2062..e50cf74cfbecd8ae3186dea02e74960865e5f010 100644 (file)
--- a/mod/quiz/report/reportlib.php
+++ b/mod/quiz/report/reportlib.php
@@ -98,7 +98,7 @@ function quiz_get_average_grade_for_questions($quiz, $userids){
                         "($qmfilter) AND " .
                         "qa.userid $usql AND " .
                         "qa.quiz = ? ".
-                        "GROUP BY qs.question";
+                        "GROUP BY qns.questionid";
     return $DB->get_records_sql_menu($questionavgssql, $params);
 }