使用Over Partition By運行Count Distinct

Question

我有一個數據集，其中包含隨時間推移購買的用戶ID。 我想顯示已經進行購買的YTD不同用戶數，按州和國家划分。 輸出將有4列：國家，州，年，月，YTD具有購買活動的不同用戶的計數。

有沒有辦法做到這一點？ 當我從視圖中排除月份並執行非常計數時，以下代碼有效：

Select Year, Country, State,
   COUNT(DISTINCT (CASE WHEN ActiveUserFlag > 0 THEN MBR_ID END)) AS YTD_Active_Member_Count
From MemberActivity
Where Month <= 5
Group By 1,2,3;

當用戶跨越多個月進行購買時會出現此問題，因為我無法按月匯總，然后匯總，因為它會重復用戶計數。

出於趨勢目的，我需要查看一年中每個月的YTD計數。

Answer 1

在用戶出現的第一個月內計算：

select Country, State, year, month,
       sum(case when ActiveUserFlag > 0 and seqnum = 1 then 1 else 0 end) as YTD_Active_Member_Count
from (select ma.*,
             row_number() over (partition by year order by month) as seqnum
      from MemberActivity ma
     ) ma
where Month <= 5
group by Country, State, year, month;

Answer 2

在購買的第一個月內，每位會員只返回一次，按月計算，然后應用累計金額：

select Year, Country, State, month,
   sum(cnt)
   over (partition by Year, Country, State
         order by month
         rows unbounded preceding) AS YTD_Active_Member_Count
from
  (
    Select Year, Country, State, month,
       COUNT(*) as cnt -- 1st purchses per month
    From 
     ( -- this assumes there's at least one new active member per year/month/country
       -- otherwise there would be mising rows 
       Select *
       from MemberActivity
       where ActiveUserFlag > 0 -- only active members
         and Month <= 5
         -- and year = 2019 -- seems to be for this year only
       qualify row_number() -- only first purchase per member/year
               over (partition by MBR_ID, year
                     order by month --? probably there's a purchase_date) = 1
     ) as dt
    group by 1,2,3,4
 ) as dt
;