Question

我在SQL Server数据库中有一个表，其中包含每次用户从我的应用程序下载图像时的注册表，因此我的表TBL_Downloads具有以下结构：

UserID|  ImageID  | DownloadDate              |
------+-----------+---------------------------+
  292 |    782    |  02-01-2016 14:20:22.737  |
  292 |    783    |  02-01-2016 14:20:22.737  |
  292 |    784    |  02-02-2016 14:20:22.737  |
  292 |    785    |  02-04-2016 14:20:22.737  |
  292 |    786    |  02-05-2016 14:20:22.737  |
  292 |    787    |  02-06-2016 14:20:22.737  |

在表中，仅显示1个特定用户的寄存器，即使有几个只是为了简化示例。

我想要的是一个结果表，其中包含特定用户在过去30天内的BY DAY下载次数，包括没有下载的日期的零。我目前有以下查询：

SELECT COUNT(*) AS Downloads
FROM TBL_Downloads
WHERE DownloadDate BETWEEN DATEADD(day, -30, GETDATE()) AND GETDATE()
  AND IdUser = 292
GROUP BY CAST(DownloadDate AS DATE)

这将返回一个包含总和的表，但仅限于至少有一个下载条目的天数。

您有什么想法我能解决这个问题吗？

Answer 1

您可以使用日历或日期表进行此类操作。

对于内存中只有152kb，您可以在表格中拥有30年的日期：

/* dates table */
declare @fromdate date = '20000101';
declare @years    int  = 30;
/* 30 years, 19 used data pages ~152kb in memory, ~264kb on disk */
;with n as (select n from (values(0),(1),(2),(3),(4),(5),(6),(7),(8),(9)) t(n))
select top (datediff(day, @fromdate,dateadd(year,@years,@fromdate)))
    [Date]=convert(date,dateadd(day,row_number() over(order by (select 1))-1,@fromdate))
into dbo.Dates
from n as deka cross join n as hecto cross join n as kilo
               cross join n as tenK cross join n as hundredK
order by [Date];
create unique clustered index ix_dbo_Dates_date
  on dbo.Dates([Date]);

如果不采取创建表格的实际步骤，您可以在common table expression内使用它：

declare @fromdate date = dateadd(day  , datediff(day  , 0, getdate() )-30 , 0); 
declare @thrudate date = dateadd(day  , datediff(day  , 0, getdate() ), 0);
;with n as (select n from (values(0),(1),(2),(3),(4),(5),(6),(7),(8),(9)) t(n))
, dates as (
  select top (datediff(day, @fromdate, @thrudate)+1) 
      [Date]=convert(date,dateadd(day,row_number() over(order by (select 1))-1,@fromdate))
  from n as deka cross join n as hecto cross join n as kilo
                cross join n as tenK cross join n as hundredK
   order by [Date]
)
select [Date]
from dates;

使用如下：

select 
    d.Date
  , count(t.DownloadDate) as DownloadCount
from dates d
  left join TBL_Downloads t
    on d.date = convert(date,t.DownloadDate)
   and t.userid = 292
where d.date >= dateadd(day  , datediff(day  , 0, getdate() )-30 , 0)
  and d.date <= dateadd(day  , datediff(day  , 0, getdate() ), 0)
group by d.date

rextester 演示：http://rextester.com/ISK37732（日期更改为过去30天内）

返回：

+------------+---------------+
|    Date    | DownloadCount |
+------------+---------------+
| 2017-02-27 |             0 |
| 2017-02-28 |             0 |
| 2017-03-01 |             2 |
| 2017-03-02 |             1 |
| 2017-03-03 |             0 |
| 2017-03-04 |             1 |
| 2017-03-05 |             1 |
| 2017-03-06 |             1 |
| 2017-03-07 |             0 |
| 2017-03-08 |             0 |
| 2017-03-09 |             0 |
| 2017-03-10 |             0 |
| 2017-03-11 |             0 |
| 2017-03-12 |             0 |
| 2017-03-13 |             0 |
| 2017-03-14 |             0 |
| 2017-03-15 |             0 |
| 2017-03-16 |             0 |
| 2017-03-17 |             0 |
| 2017-03-18 |             0 |
| 2017-03-19 |             0 |
| 2017-03-20 |             0 |
| 2017-03-21 |             0 |
| 2017-03-22 |             0 |
| 2017-03-23 |             0 |
| 2017-03-24 |             0 |
| 2017-03-25 |             0 |
| 2017-03-26 |             0 |
| 2017-03-27 |             0 |
| 2017-03-28 |             0 |
| 2017-03-29 |             0 |
+------------+---------------+

数字和日历表参考：

Answer 2

您可以使用group by查找计数并使用公用表格

生成日期

--Final Query - For this query to execute you require #dates to be populated as below
select cte_start_date as [date], coalesce(cnt,0) as DownLoadCount from #dates d left join
(
    select userid,convert(date,DownloadDate) dt , count( convert(date,DownloadDate)) as cnt from #yourDownloads
    group by userid, convert(date,DownloadDate)
) a
on d.cte_start_date = a.dt

用于填充该月日期的公用表表达式递归查询

--Populuating dates
declare @start_date date = '02-01-2016'
declare @end_date date = eomonth('02-01-2016')
;WITH CTE AS
(
    SELECT @start_date AS cte_start_date
    UNION ALL
    SELECT DATEADD(DAY, 1, cte_start_date)
    FROM CTE
    WHERE DATEADD(DAY, 1, cte_start_date) <= @end_date    
)
select * into #dates from cte

您的输入表

create table #yourDownloads (UserId int, ImageId int, DownloadDate datetime)

insert into #yourDownloads 
( UserID ,  ImageID , DownloadDate  ) values
 (  292 ,  782   ,'02-01-2016 14:20:22.737')
,(  292 ,  783   ,'02-01-2016 14:20:22.737')
,(  292 ,  784   ,'02-02-2016 14:20:22.737')
,(  292 ,  785   ,'02-04-2016 14:20:22.737')
,(  292 ,  786   ,'02-05-2016 14:20:22.737')
,(  292 ,  787   ,'02-06-2016 14:20:22.737')

按天计数寄存器，包括零

2 个答案: