题解 | #每个题目和每份试卷被作答的人数和次数#
每个题目和每份试卷被作答的人数和次数
http://www.nowcoder.com/practice/203d0aed8928429a8978185d9a03babc
SELECT exam_id AS tid, COUNT(DISTINCT uid) AS uv, COUNT(*) AS pv
FROM exam_record
GROUP BY exam_id
UNION ALL
SELECT question_id AS tid, COUNT(DISTINCT uid) AS uv, COUNT(*) AS pv
FROM practice_record
GROUP BY question_id
ORDER BY LEFT(tid,2) DESC, uv DESC, pv DESC;
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