选择应用类别 (category) 和计算中位数决策时间，并将其命名为 median_decision_time

SELECT m.category, CAST( PERCENTILE_CONT(0.5) WITHIN GROUP (ORDER BY TIMESTAMPDIFF(SECOND, a.time, d.time)) AS UNSIGNED ) AS median_decision_time FROM app a # 将 app 表与 mapping_table 表连接，根据 package_name 进行匹配 JOIN mapping_table m ON a.package_name = m.package_name # 用子查询查找每个用户下载每个应用的最早时间 JOIN ( SELECT userid, package_name, MIN(time) AS time FROM app WHERE action_type = 'download' GROUP BY userid, package_name ) AS d ON a.userid = d.userid AND a.package_name = d.package_name

选择 action_type 为 'itemShow' 的记录

WHERE a.action_type = 'itemShow'

按照应用类别 (category) 进行分组

GROUP BY m.category