查询滚动日期范围内的不同值的计数

Question

我有一组电子邮件地址和日期,这些电子邮件地址已添加到表格中.对于不同的日期,可以有多个电子邮件地址条目.例如,如果我有下面的数据集.我希望得到我们在所述日期和3天前之间的不同电子邮件的日期和计数.

Date   | email  
-------+----------------
1/1/12 | test@test.com
1/1/12 | test1@test.com
1/1/12 | test2@test.com
1/2/12 | test1@test.com
1/2/12 | test2@test.com
1/3/12 | test@test.com
1/4/12 | test@test.com
1/5/12 | test@test.com
1/5/12 | test@test.com
1/6/12 | test@test.com
1/6/12 | test@test.com
1/6/12 | test1@test.com

如果我们使用3的日期,结果集看起来会像这样

date   | count(distinct email)
-------+------
1/1/12 | 3
1/2/12 | 3
1/3/12 | 3
1/4/12 | 3
1/5/12 | 2
1/6/12 | 2

我可以使用下面的查询获得日期范围的明确计数,但是希望按天计算范围,这样我就不必手动更新数百个日期的范围.

select test.date, count(distinct test.email)  
from test_table as test  
where test.date between '2012-01-01' and '2012-05-08'  
group by test.date;

感谢帮助.

Answer 1

测试用例:

CREATE TEMP TABLE tbl (day date, email text);
INSERT INTO tbl VALUES
 ('2012-01-01', 'test@test.com')
,('2012-01-01', 'test1@test.com')
,('2012-01-01', 'test2@test.com')
,('2012-01-02', 'test1@test.com')
,('2012-01-02', 'test2@test.com')
,('2012-01-03', 'test@test.com')
,('2012-01-04', 'test@test.com')
,('2012-01-05', 'test@test.com')
,('2012-01-05', 'test@test.com')
,('2012-01-06', 'test@test.com')
,('2012-01-06', 'test@test.com')
,('2012-01-06', 'test1@test.com`');

查询 - 仅返回条目存在于的tbl日期:

SELECT day
     ,(SELECT count(DISTINCT email)
       FROM   tbl
       WHERE  day BETWEEN t.day - 2 AND t.day -- period of 3 days
      ) AS dist_emails
FROM   tbl t
WHERE  day BETWEEN '2012-01-01' AND '2012-01-06'  
GROUP  BY 1
ORDER  BY 1;

或者 - 返回指定范围内的所有日期,即使当天没有行:

SELECT day
     ,(SELECT count(DISTINCT email)
       FROM   tbl
       WHERE  day BETWEEN g.day - 2 AND g.day
      ) AS dist_emails
FROM  (SELECT generate_series('2012-01-01'::date
                            , '2012-01-06'::date, '1d')::date) AS g(day)

结果:

day        | dist_emails
-----------+------------
2012-01-01 | 3
2012-01-02 | 3
2012-01-03 | 3
2012-01-04 | 3
2012-01-05 | 1
2012-01-06 | 2

这听起来像是一个窗口函数的工作,但我没有找到一种方法来定义合适的窗口框架.另外,根据文件:

与普通聚合函数不同,聚合窗口函数不允许DISTINCT或ORDER BY在函数参数列表中使用.

所以我用相关的子查询解决了它.我猜这是最聪明的方式.

我将您的日期列重命名为day,因为使用类型名称作为标识符是不好的做法.

顺便说一句,"在所述日期和3天前之间"将是4天的时间段.你的定义在那里是矛盾的.

有点短,但只有几天慢:

SELECT day, count(DISTINCT email) AS dist_emails
FROM  (SELECT generate_series('2013-01-01'::date
                            , '2013-01-06'::date, '1d')::date) AS g(day)
LEFT   JOIN tbl t ON t.day BETWEEN g.day - 2 AND g.day
GROUP  BY 1
ORDER  BY 1;

Answer 2

在 SQL Server 中：

`select test.date, count(distinct test.email) from test_table as test  where convert(date,test.date) between '2012-01-01' and '2012-05-08' group by test.date`

希望这可以帮助。