题解 | #大小写混乱时的筛选统计#
大小写混乱时的筛选统计
https://www.nowcoder.com/practice/81cb12931a604811ae69d332515c7734
WITH t_tag_count as (
SELECT tag, COUNT(uid) as answer_cnt
FROM exam_record
JOIN examination_info USING(exam_id)
GROUP BY tag
)
select a.tag,b.answer_cnt from t_tag_count as a, t_tag_count as b where
upper(a.tag) = b.tag AND a.tag != b.tag AND a.answer_cnt < 3
本题只要通过自连接，将表a的tag upper后与b一致，求出a.tag和b.answer_cnt即可
