select t.job, case when t.num%2=0 then round(t.num/2,0) else round((t.num+1)/2,0) end 'start', case when t.num%2=0 then round(t.num/2+1,0) else round((t.num+1)/2,0) end 'end' from (select job,count(score) num from grade group by job)t order by t.job