第五题sql怎么写啊我写的select case when year(birth)>=1990 and year(birth)<2000 then '90 后' when year(birth)>=2000 and year(birth)<2010 then '00 后' end as 年龄段, sum(余额字段)(忘了) as '余额' from xxx,xxxwhere xxx xxx group by 年龄段测试通过了,但是提交它显示0%