select distinct job, case when (count(*) over(partition by job))%2=1 then round(((count(*) over(partition by job))-1)/2+1,0) else round(((count(*) over(partition by job))-1)/2,0) end as 'start', case when (count(*) over(partition by job))%2=1 then round(((count(*) over(partition by job))-1)/2+1,0) else round((count(*) over(partition by job))/2+1,0) end as 'end' from grade order by job