Fix prefix of tables

classes/local/exporter.php

@@ -190,9 +190,9 @@ class exporter {
         $sql = "SELECT DISTINCT u.email
               FROM {user} u
               JOIN {role_assignments} ra ON u.id=ra.userid
-              JOIN mdl_user_enrolments e ON e.userid=u.id
-              JOIN mdl_role r ON ra.roleid=r.id
-              JOIN mdl_context c ON ra.contextid=c.id
+              JOIN {user_enrolments} e ON e.userid=u.id
+              JOIN {role} r ON ra.roleid=r.id
+              JOIN {context} c ON ra.contextid=c.id
              WHERE c.contextlevel= :contextlevel
                AND e.status = :enrolment_status
                    AND u.deleted = :user_deleted