题解 | #大小写混乱时的筛选统计#
大小写混乱时的筛选统计
http://www.nowcoder.com/practice/81cb12931a604811ae69d332515c7734
select t1.tag,t2.cnt
from (
select e1.tag,count(*) as cnt
from exam_record as e2 left join examination_info as e1
on e1.exam_id = e2.exam_id group by e1.tag ) t1
inner join
(select e1.tag,count(*) as cnt
from exam_record as e2 left join examination_info as e1
on e1.exam_id = e2.exam_id group by e1.tag ) t2
on upper(t1.tag) = t2.tag
and t1.tag != t2.tag
and t1.cnt <= 3
