Question

我的mysql数据库中有下表。

user_id| department | comment_time
-----------------------------------------
ahnaf  |     OM1    | 2018-02-01 10:00:00
muttaki|     OM2    | 2018-02-01 11:00:00
sunny  |     OM3    | 2018-02-01 12:00:00
ahnaf  |     OM1    | 2018-02-01 21:00:00
john   |     OM2    | 2018-02-01 23:00:00

我想从此表中找出部门中某人发表评论的频率。我正在寻找这样的答案：OM1中的一个人平均每5分钟评论一次。

我不知道如何为此编写查询。

Answer 1

您可以通过将总跨度除以评论数减去一来获得评论之间的平均间距：

select department,
       ( ( to_seconds(max(comment_time)) - to_seconds(min(comment_time))
         ) / nullif(count(*) - 1, 0)
       ) / 60 as avg_comment_in_minutes
from t
group by department;

如果您知道这些评论是最新的，并且您想处理自最近的评论以来的时间跨度，则可以执行以下操作：

select department,
       ( ( to_seconds(now()) - to_seconds(min(comment_time))
         ) / count(*)
       ) / 60 as avg_comment_in_minutes
from t
group by department;

Answer 2

请尝试这个

SELECT user_id,department, FROM_UNIXTIME(AVG(UNIX_TIMESTAMP(comment_time))) as average_time 
FROM dept 
GROUP by user_id

我使用表名作为部门

Answer 3

尝试

select department, avg(diff_comment_time) FROM (select department, LAG(comment_time) OVER ( PARTITION BY department ORDER BY comment_time DESC) - comment_time as diff_comment_time from test) test2 group by department

如何从单个datetime列获取平均间隔？

3 个答案: