CourseParticipantsExporter: fixed export with group-id or group name enabled

classes/exporters/CourseParticipantsExporter.php

@@ -287,7 +287,9 @@ class CourseParticipantsExporter extends Exporter
 
         if ($with_group_id || $with_group_name) {
             $joins_sql[] = 'LEFT JOIN `statusgruppen`
-                ON `seminar_user`.`Seminar_id` = `statusgruppen`.`range_id`';
+                ON `seminar_user`.`Seminar_id` = `statusgruppen`.`range_id`
+                LEFT JOIN `statusgruppe_user`
+                USING (`statusgruppe_id`)';
         }
 
         if ($min_participants > 0) {
@@ -303,11 +305,13 @@ class CourseParticipantsExporter extends Exporter
 
         if ($with_first_name || $with_last_name || $with_email) {
             $with_user_data = true;
-            $joins_sql[] = 'INNER JOIN `auth_user_md5` USING (`user_id`)';
+            $joins_sql[] = 'INNER JOIN `auth_user_md5`
+                ON `seminar_user`.`user_id` = `auth_user_md5`.`user_id`';
         }
         if ($with_title_front || $with_title_after || $with_salutation) {
             $with_user_info_data = true;
-            $joins_sql[] = 'INNER JOIN `user_info` USING (`user_id`)';
+            $joins_sql[] = 'INNER JOIN `user_info`
+                ON `seminar_user`.`user_id` = `user_info`.`user_id`';
         }
         if ($semester_id || $institute_id || $with_course_name
             || $with_course_number || $with_course_type_id