明确题意：

统计每个题目和每份试卷被作答的人数和次数，分别在试卷区和题目区按uv & pv降序显示

问题分解：

• 统计每份试卷被作答的人数和次数，生成子表t_exam_uv_pv：
  • 从exam_record抽出每条记录的试卷ID和用户ID
  • 按试卷ID分组：GROUP BY exam_id
  • 计算uv：count(distinct uid) uv
  • 计算pv：count(uid) as pv
• 统计每个题目被作答的人数和次数，生成子表t_practice_uv_pv：
  • 从practice_record抽出每条记录的试题ID和用户ID
  • 按试卷ID分组：GROUP BY question_id
  • 计算uv：count(distinct uid) uv
  • 计算pv：count(uid) as pv
• 合并上面记录：UNION ALL

细节问题：

• 表头重命名：as
• 分别按uv & pv降序：ORDER BY uv desc, pv desc

完整代码：

SELECT tid, uv, pv FROM (
    SELECT exam_id as tid, count(distinct uid) uv, count(uid) as pv
    FROM exam_record
    GROUP BY exam_id
    ORDER BY uv desc, pv desc
) as t_exam_uv_pv
UNION ALL
SELECT tid, uv, pv FROM (
    SELECT question_id as tid, count(distinct uid) uv, count(uid) as pv
    FROM practice_record
    GROUP BY question_id
    ORDER BY uv desc, pv desc
) as t_practice_uv_pv;