sql中除法的插入问题并显示

Question

sql 基本语句为 ：
select StationName,entryspotname,exambatchcode,
count(examstudentid) as ykrs,-- [应考人数],
count(case when UnNormalCode<>2 and Ismodifide=1 then achstudentid end ) as skrs--[实考人数]
from v_exam
group by StationID,StationName, EntrySpotId,entryspotname,ExamBatchID,exambatchcode
order by StationID,StationName, EntrySpotId,entryspotname,ExamBatchID,exambatchcode;

要求
表列有StationName, entryspotname, exambatchcode，应考人数，实考人数，流失率，

不知道流失率对应的语句如何写进刚才的sql语句，并在表中有对应的列

Answer 1

select skrs,ykrs,round(skrs/ykrs,2) as c from v_exam 这个就是流失率