select grg,sum(cnt)
from (
select left(class,2) as grd,count(*) as cnt
from 表a 
where score>=60
group by left(class,2)
union all
select '初一',0
union all
select '初二',0
union all
select '初三',0
)

------解决方案--------------------

探讨

3楼好像运行不能通过