明确题意：

找到昵称以『牛客』开头『号』结尾、成就值在1200~2500之间且最近一次活跃（答题或作答试卷）在2021年9月的用户信息

问题分解：

• 筛选用户条件：
  • 昵称以『牛客』开头『号』结尾：WHERE nick_name LIKE "牛客%号"
  • 成就值在1200~2500之间：achievement BETWEEN 1200 AND 2500
  • 最近一次活跃（答题或作答试卷）在2021年9月：
    • 生成用户每次活跃月份：
      • 试卷区活跃情况：SELECT distinct uid, DATE_FORMAT(start_time, "%Y%m") as active_month
      • 练习区活跃情况：SELECT distinct uid, DATE_FORMAT(submit_time, "%Y%m") as active_month
      • 合并活跃情况：UNION
    • 按用户分组：GROUP BY uid
    • 筛选最近一次活跃月份：HAVING MAX(active_month)="202109"

细节问题：

• 表头重命名：as

完整代码：

SELECT uid, nick_name, achievement
FROM user_info
WHERE nick_name LIKE "牛客%号" and achievement BETWEEN 1200 AND 2500 AND uid IN (
    SELECT uid
    FROM (
        SELECT distinct uid, DATE_FORMAT(start_time, "%Y%m") as active_month
        FROM exam_record
        UNION
        SELECT distinct uid, DATE_FORMAT(submit_time, "%Y%m") as active_month
        FROM practice_record
    ) as t_uid_active_month
    GROUP BY uid
    HAVING MAX(active_month)="202109"
);