SELECT job, CASE WHEN COUNT(job)%2=0 THEN TRUNCATE(COUNT(job)/2,0) ELSE TRUNCATE(FLOOR(COUNT(job)/2)+1,0) END start , CASE WHEN COUNT(job)%2=0 THEN TRUNCATE(COUNT(job)/2,0)+1 ELSE TRUNCATE(FLOOR(COUNT(job)/2)+1,0) END end FROM grade GROUP BY job ORDER BY job ASC