select job,case when count(id)%2=0 then round(count(id)/2,0) when count(id)%2=1 then round((count(id)+1)/2,0) end as start, case when count(id)%2=0 then round((count(id)/2)+1,0) when count(id)%2=1 then round((count(id)+1)/2,0) end as end from grade group by job order by job asc