题解 | #考试分数(四)#

with t as (select job,count(score) as num from grade 
group by job)
select job
     , ceil(num/2) as start
     , if(num%2=0,ceil(num/2)+1,ceil(num/2)) as end
   from t 
order by job

方法很多：if（条件表达式，满足条件的结果，不满足条件的返回值）简单

ceil（）向上取整，floor（）向下取整

注意：start时：无论是奇数还是偶数都一样ceil(num/2)：ceil(num/2) as start

end时分情况，偶数是ceil(num/2)+1，奇数时ceil(num/2)：if(num%2=0,ceil(num/2)+1,ceil(num/2)) as end