1)select recno, class, timetable_idx, center, course, ibt_setno, SUBSTR(test_ym, 5, 2) as test_ym, test_day from class_table where test_ym IS NOT NULL and test_ym = '202601' and test_day = '27' and time_start <= 15 group by recno, class, timetable_idx, center, course, ibt_setno, test_ym order by recno desc limit 10
