相关疑难解决方法(0)

我正在计算在 Stack Overflow 上得到回复的平均时间，结果毫无意义。

#standardSQL

WITH question_answers AS (
  SELECT * 
    , timestamp_diff(answers.first, creation_date, minute) minutes
  FROM (
    SELECT creation_date
      , (SELECT AS STRUCT MIN(creation_date) first, COUNT(*) c
         FROM `bigquery-public-data.stackoverflow.posts_answers` b
         WHERE a.id=b.parent_id
        ) answers
      , SPLIT(tags, '|') tags
    FROM `bigquery-public-data.stackoverflow.posts_questions` a
    WHERE EXTRACT(year FROM creation_date) > 2015
  ), UNNEST(tags) tag
  WHERE tag IN ('java', 'javascript', 'google-bigquery', 'firebase', 'php')
  AND answers.c > 0
)

SELECT tag
  , COUNT(*) questions
  , ROUND(AVG(minutes), 2) first_reply_avg_minutes
FROM question_answers
GROUP BY tag

我应该如何计算平均时间？