SELECT ec.fullname,
       (CASE
            WHEN uce.rolearchetype = 'editingteacher' THEN array_to_string(array_agg(DISTINCT(uce.username)), ', ')
        END) AS editing_teachers,
       (CASE
            WHEN uce.rolearchetype = 'teacher' THEN array_to_string(array_agg(DISTINCT(uce.username)), ', ')
        END) AS non_editing_teachers
FROM e_course ec
JOIN e_user_course_enrolments uce ON ec.id = uce.courseid
WHERE ec.id = '7545'
GROUP BY ec.fullname, uce.rolearchetype