SQL Server:即使某些天没有数据,如何选择日期范围内的所有日期

Question

我有一个应用程序需要显示过去30天内的活动条形图.即使当天没有任何活动,图表也需要显示所有日期.

例如:

DATE       COUNT
==================
1/1/2011   5 
1/2/2011   3 
1/3/2011   0
1/4/2011   4
1/5/2011   0
etc....

我可以在查询之后进行后期处理以找出缺少的日期并添加它们但是想知道在SQL Server中是否有更简单的方法.非常感谢

Answer 1

您可以使用递归CTE来构建30天的列表,然后将其加入到您的数据中

--test
select cast('05 jan 2011' as datetime) as DT, 1 as val into #t
union all select CAST('05 jan 2011' as datetime), 1 
union all select CAST('29 jan 2011' as datetime), 1 

declare @start datetime = '01 jan 2011'
declare @end   datetime = dateadd(day, 29, @start)

;with amonth(day) as
(
    select @start as day
        union all
    select day + 1
        from amonth
        where day < @end
)
select amonth.day, count(val)
    from amonth 
    left join #t on #t.DT = amonth.day
group by amonth.day


>>

2011-01-04 00:00:00.000 0
2011-01-05 00:00:00.000 2
2011-01-06 00:00:00.000 0
2011-01-07 00:00:00.000 0
2011-01-08 00:00:00.000 0
2011-01-09 00:00:00.000 0
...

Answer 2

使用CTE:

WITH DateTable
AS
(
    SELECT CAST('20110101' AS Date) AS [DATE]
    UNION ALL
    SELECT DATEADD(dd, 1, [DATE])
    FROM DateTable
    WHERE DATEADD(dd, 1, [DATE]) < cast('20110201' as Date)
)
SELECT dt.[DATE], ISNULL(md.[COUNT], 0) as [COUNT]
FROM [DateTable] dt
LEFT JOIN [MyData] md
ON md.[DATE] = dt.[DATE]

这假设一切都是日期; 如果它是DateTime,你将不得不截断(with DATEADD(dd, 0, DATEDIFF(dd, 0, [DATE]))).

Answer 3

@Alex K. 的答案是完全正确的，但它不适用于不支持递归公用表表达式的版本（例如我正在使用的版本）。在这种情况下，以下将完成这项工作。

DECLARE @StartDate datetime = '2015-01-01'
DECLARE @EndDate datetime = SYSDATETIME()

;WITH days AS
(
  SELECT DATEADD(DAY, n, DATEADD(DAY, DATEDIFF(DAY, 0, @StartDate), 0)) as d
    FROM ( SELECT TOP (DATEDIFF(DAY, @StartDate, @EndDate) + 1)
            n = ROW_NUMBER() OVER (ORDER BY [object_id]) - 1
           FROM sys.all_objects ORDER BY [object_id] ) AS n
)
select days.d, count(t.val)
    FROM days LEFT OUTER JOIN yourTable as t
    ON t.dateColumn >= days.d AND t.dateColumn < DATEADD(DAY, 1, days.d)
GROUP BY days.d
ORDER BY days.d;