Question

我需要计算应用使用期限的每周平均值（每次使用都有自己的持续时间日志）。问题是我想比较某个事件发生之前和之后的平均值（每个用户的不同日期）。因此，如果事件发生在一个月前的星期二，我想计算在特定星期二之前和之后的星期二开始的每周平均值。

相关数据如下：事件

User ID || date of event
3fin2d..|| 19/03/17
2f4j34..|| 20/03/17

USAGE

UID      || timestamp start   ||  timestamp end      || Duration
3fin2d.. || 11/03/17 11:20:00 ||  11/03/17 12:00:00  ||   00:40
3fin2d.. || 18/03/17 11:20:00 ||  18/03/17 12:00:00  ||   00:40
2f4j34.. || 19/03/17 18:20:00 ||  19/03/17 18:40:00  ||   00:20
2f4j34.. || 19/03/17 19:20:00 ||  19/03/17 20:00:00  ||   00:40
3fin2d.. || 19/03/17 19:30:00 ||  19/03/17 20:00:00  ||   00:30
2f4j34.. || 20/03/17 19:20:00 ||  20/03/17 20:00:00  ||   00:40

编辑：用户

UID        || Created On
3fin2d..   || 11/03/17 11:00:00
2f4j34..   || 18/03/17 13:00:00

预期结果：

UID      ||Average Duration before even||Average Duration After event 
3fin2d.. ||            00:40:00        ||    00:30:00
2f4j34.. ||            01:00:00        ||    00:40:00

当然应考虑使用0周的周数。在上面的例子中，我假设当前日期是20/03/17（否则应该计算更多的零）。

谢谢

Answer 1

http://rextester.com/USBJ20378

select uid,
    avg(u.duration) filter (where usage_start < e.event_date) as before,
    avg(U.duration) filter (where usage_start >= e.event_date) as after
from
    usage u
    inner join
    events e using (uid)
where usage_start between e.event_date - 7 and e.event_date + 7
group by uid
;
  uid   |  before  |  after   
--------+----------+----------
 2f4j34 | 00:30:00 | 00:40:00
 3fin2d | 00:40:00 | 00:30:00

每周平均值从不同日期开始 - postgresql

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