从查询中插入缺失的日期

Question

如何从我创建的查询中插入缺失的日期。结果如下：

Date          Frequency
2014-05-18    5
2014-05-20    7
2014-05-25    7
2014-05-27    6

我希望结果缺少值为 0 的日期，如下所示：

Date          Frequency
2014-05-18    5
2014-05-19    0
2014-05-20    7
2014-05-21    0
2014-05-22    0
2014-05-23    0
2014-05-24    0
2014-05-25    7
2014-05-26    0
2014-05-27    6

请注意，我对服务器具有只读访问权限。

Answer 1

这是一个使用日历表的示例（您确实应该拥有）。此示例仅填充 2014 年，但您可以根据需要填充任意数量的年份...

CREATE TABLE dbo.Calendar(d DATE PRIMARY KEY);

INSERT dbo.Calendar(d) SELECT TOP (365)
 DATEADD(DAY, ROW_NUMBER() OVER (ORDER BY number)-1, '20140101')
 FROM [master].dbo.spt_values
 WHERE [type] = N'P' ORDER BY number;

现在查询很简单：

DECLARE @s DATE = '20140518', @e DATE = '20140527';

SELECT c.d, Frequency = COALESCE(s.Frequency,0)
  FROM dbo.Calendar AS c
  LEFT OUTER JOIN dbo.splunge AS s
  ON c.d = s.[date]
  WHERE c.d >= @s
    AND c.d < DATEADD(DAY, 1, @e);

SQLfiddle 示例

如果您无法创建日历表（并且手头也没有数字表），那么您可以将其内联：

DECLARE @s DATE = '20140518', @e DATE = '20140527';

SELECT c.d, Frequency = COALESCE(s.Frequency,0)
  FROM 
(
   SELECT TOP (DATEDIFF(DAY, @s, @e)+1)
 DATEADD(DAY, ROW_NUMBER() OVER (ORDER BY number)-1, @s)
 FROM [master].dbo.spt_values
 WHERE [type] = N'P' ORDER BY number
) AS c(d)
  LEFT OUTER JOIN dbo.splunge2 AS s
  ON c.d = s.[date]
  WHERE c.d >= @s
    AND c.d < DATEADD(DAY, 1, @e);

SQLfiddle 示例

有关生成集（日期、数字等）的更多信息，请参阅本系列：

• http://sqlperformance.com/generate-a-set-1
• http://sqlperformance.com/generate-a-set-2
• http://sqlperformance.com/generate-a-set-3