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