关于（另一个）SQL查询的帮助

Question

继我之前的question。

我有一个名为activity有2列的表格：

`when` as datetime // last time i saw a user 
guid as varchar // a unique identifier for each user 

我有一个返回值有多少新用户对于给定的日期和时间跨度的查询：

SET @till_date='2009-11-01'; #for today, give CURDATE()+1 
SET @duration=1; # this can be changed to 7, 31, etc 
SELECT COUNT(guid) AS total_new_users, DATE_SUB(@till_date, INTERVAL @duration DAY) AS since_date, @till_date AS till_date 
FROM `activity` WHERE 1 
    AND `when` BETWEEN DATE_SUB(@till_date, INTERVAL @duration DAY) AND @till_date 
    AND guid NOT IN 
    (
    SELECT guid 
    FROM `activity` 
    WHERE `when` < DATE_SUB(@till_date, INTERVAL @duration DAY) 
) 

我想能够构建一个查询，该查询将在给定的时间范围内返回每个日期的新用户列表。这将被用来建立每天的新用户一个月，一周，图表等

事情是这样的：

total_new_users | since_date | till_date 
---------------------------------------------- 
    10   | 2009-11-20 | 2009-11-21 
    10   | 2009-11-21 | 2009-11-22 
    10   | 2009-11-22 | 2009-11-23 

我想过使用UNION与LOOP，但我的SQL知识相当基本的，帮助？

---

结果（感谢@pilcrow）：

SET @till_date='2009-11-15'; 
SET @since_date='2009-11-01'; 
SELECT first AS yyyymmdd, 
    COUNT('x') AS new_user_count 
FROM (SELECT guid, 
      DATE(MIN(`when`)) AS first 
     FROM activity 
     GROUP BY 1) first_appearance 
WHERE first BETWEEN @since_date AND @till_date 
GROUP BY 1 

Answer 1

。假定SET SESSION的sql_mode = 'ANSI_QUOTES'：

SELECT first AS yyyymmdd, 
     COUNT('x') AS new_user_count 
FROM (SELECT guid, 
      MIN("when") AS first 
     FROM activity 
     GROUP BY 1) first_appearance 
WHERE first BETWEEN @since_date AND @till_date 
GROUP BY 1 

你当然可以用DATE_SUB()代替@since_date，如果你喜欢。

Answer 2

SELECT 
    COUNT(DISTINCT guid) AS total_new_users, 
    DATE(when) AS since_date, 
    DATE(DATE_ADD(when, INTERVAL 1 DAY)) AS till_date 
FROM 
    Activity 
GROUP BY 
    DATE(when)