在過去的三週時間段內獲取總數

Question

我有一個（說）用戶的大表以及他們訪問各種網頁的情況。該表的一個例子是：

schema.page_views 

     date| user_id|   webpage| 
----------+---------+----------------+ 
01/05/2012|aaaaaaaaa|www.example1.com| 
01/06/2012|aaaaaaaaa|www.example2.com| 
01/06/2012|ababababa|www.example1.com| 
        ... 
01/05/2013|aaaaaaaaa|www.example2.com| 
01/05/2013|ababababa|www.example1.com| 
03/05/2013|aaaaaaaaa|www.example2.com| 

另外，我有一個日曆查找表：

schema.weeks 

week_number| begin_date| end_date|year| 
-----------+-----------+-----------+----+ 
     18| 2012-04-23| 2012-04-30|2012| 
     17| 2012-04-15| 2012-04-22|2012| 
     16| 2012-04-08| 2012-04-14|2012| 

我最終會由這兩個表喜歡的是一個後置三個周累計的頁面訪問量。更具體地講，如果我今天發出此查詢，我想沿着線的東西：

  webpage| 1-3| 4-6| 7-9| 10-12| 
----------------+-------+-------+-------+-------+ 
www.example1.com| 124875| 175682| 168542| 159780| 
www.example2.com| three week period numbers | 

其中「1-3」是指最近的三個星期裏，「4-6」是指四六個星期前，等

到目前爲止，我已經得到了各個網站和每週每週的總頁面瀏覽，如下：

-- join to get begin and end_dates 
with t1 as (
select a.*, b.* from schema.page_views a 
join schema.weeks b 
on a.date between b.begin_date and b.end_date), 

-- now aggregate per week 
weekly_vol as (
select webpage, year, week_number, begin_date, end_date, 
count(*) volume 
from t1 
group by 1, 2, 3, 4, 5) 

select * from weekly_vol limit 1; 

給出，例如，

  webpage| year| week_number| begin_date| end_date| volume| 
----------------+-----+------------+-----------+-----------+-------+ 
www.example1.com| 2012|   18| 2012-04-23| 2012-04-30| 41871| 

用這樣的表格，我怎麼能到我想要的桌子？我曾想過用on a.week_number between b.week_number and b.week_number + 2之類的東西加入它，但我不認爲這個想法在過去的12周包括新的一年的開始時將起作用。

有沒有人做過類似的事情？如果是的話，你是如何處理這個問題的？對於不同方法的建議，我們將同樣讚賞。

Answer 1

你的問題有點不清楚。週數是在一年內還是在所有時間？你想要數據中相對於上週的數額還是相對於當前日期？

在任何情況下，下面的內容至少與你想要的相似。關鍵是外部查詢中的條件聚合：

with t1 as (
     select pv.*, w.*, 
      max(pv.week_number) over (partition by webpage, year) as last_week_number 
     from schema.page_views pv join 
      schema.weeks w 
      on pv.date between w.begin_date and w.end_date 
    ), 
    weekly_vol as (
     select webpage, year, week_number, begin_date, end_date, 
      count(*) as volume 
     from t1 
     group by webpage, year, week_number, begin_date, end_date 
    ) 
select webpage, year, 
     sum(case when last_week_number - week_number < 3 
       then volume else 0 
      end) as week_1_3, 
     sum(case when last_week_number - week_number >= 3 and last_week_number - week_number < 6 
       then volume else 0 
      end) as week_4_6 
from weekly_vol 
group by webpage, year;