按日期累計計數問題

Question

我有一張表格，顯示每個日期的客戶ID列表 - 顯示在特定日期活躍的客戶。所以每個日期都可以包含也存在於另一個日期的id。

bdate   customer_id 
2012-01-12  111 
2012-01-13  222 
2012-01-13  333 
2012-01-14  111 
2012-01-14  333 
2012-01-14  666 
2012-01-14  777 

我期待寫一個計算的唯一ID的兩個日期之間的總數查詢 - 起始日期是行日期和結束日期在未來的某個特定日期。

我的查詢看起來是這樣的：

select 
    bdate, 
    count(distinct customer_id) as cts 
from users 
where bdate between bdate and current_date 
group by 1 
order by 1 

但是，這會產生獨特的用戶的數量對於每一日期，就像這樣：

bdate   customer_id 
2012-01-12  1 
2012-01-13  2 
2012-01-14  4 

我期望的結果是（爲起點之間的用戶的數量排日期和2012-01-14）

bdate   customer_id 
2012-01-12  5 - includes (111,222,333,666,777) 
2012-01-13  5 - includes (222,333,111,666,777) 
2012-01-14  4 - includes (111,333,666,777) 

Answer 1

贊@Strawberry說，你可以做一個加入這樣的：

select 
    t1.bdate, 
    count(distinct t2.customer_id) as cts 
from users t1 
join users t2 on t2.bdate >= t1.bdate 
where t1.bdate between t1.bdate and current_date 
group by t1.bdate 
order by t1.bdate 

加入T2可以讓你所有特殊的日子和current_date之間的用戶，然後count T2的customer_id，僅此而已。

SqlFiddle Demo Here