mysql 不及格率

select name, 

       100*sum(case 

                    when mark>=60 

                    then 1 else 0 

                end)/count(*) 及格率 

from score 

group by name

select convert(varchar(10),sum(case when (html+sql)/2>=60 and (html+sql)/2<80 then 1 else 0 end)*100.0/

stucount)+'%' as 及格率,

convert(varchar(10),sum(case when (html+sql)/2>=80 then 1 else 0 end)*100.0/stucount)+'%' as 优秀率

from exam e,(select count(1) as stucount from stuinfo) a

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