sql - SQL 拆分日期

Question

我想用 StartTime 和 StopTime 将表的每一行拆分为天。

例子：

User    Site    Title    TimeStampStart(01-11-2013)    TimeStampStop(05-11-2013)

我想在间隔中获得五行作为时间戳：

User    Site    Title    TimeStampStart(01-11-2013)
User    Site    Title    TimeStampStart(02-11-2013)
User    Site    Title    TimeStampStart(03-11-2013)
User    Site    Title    TimeStampStart(04-11-2013)
User    Site    Title    TimeStampStart(05-11-2013)

我创建了一个 ListDates 函数，它允许我从两个时间戳中拆分天数，但我不能使用它，因为我需要使用表作为参数。

Answer 1

如果你有一个数字表，这是相当微不足道的。

CREATE TABLE dbo.Numbers(n INT PRIMARY KEY);

INSERT dbo.Numbers(n) SELECT TOP (1000) rn = ROW_NUMBER() OVER 
  (ORDER BY [object_id]) FROM sys.all_objects;

-- if you may have dates that may be more than 1000 days apart (~3 years), 
-- increase TOP and use a cross join against one of the other system views

然后：

SELECT s.Site, DATEADD(DAY, n.n, TimeStampStart)
FROM dbo.YourTable AS s
INNER JOIN dbo.Numbers AS n
ON n.n <= DATEDIFF(DAY, s.TimeStampStart, s.TimeStampStop);

SQLFiddle 演示

生成集的许多示例（以及为什么数字表通常效果最好）：

http://sqlperformance.com/generate-a-set-1

http://sqlperformance.com/generate-a-set-2

http://sqlperformance.com/generate-a-set-3

Answer 2

您可以使用系统表 Master..spt_values 获取整数的顺序列表，并将其连接到您的源，每次将整数添加到开始日期（并在结束日期停止）。例如

DECLARE @T TABLE (TimestampStart DATETIME2, TimestampStop DATETIME2);
INSERT @T VALUES ('20131101', '20131105');

SELECT  Date = DATEADD(DAY, spt.Number, t.TimeStampStart)
FROM    @t t
        INNER JOIN master..spt_values spt
            ON spt.Number <= DATEDIFF(DAY, t.TimestampStart, t.TimestampStop)
            AND spt.Type = 'P';

如果您担心 Microsoft 会删除“未记录”表格Master..spt_values，或者您的日期相隔超过 2047 天，您可以通过另一种方式生成数字列表：

DECLARE @T TABLE (TimestampStart DATETIME2, TimestampStop DATETIME2);
INSERT @T VALUES ('20131101', '20131105');

WITH Numbers AS 
(   SELECT  TOP 100000 Number = ROW_NUMBER() OVER(ORDER BY a.Object_ID) - 1
    FROM    sys.all_objects a
            CROSS JOIN sys.all_objects b
)
SELECT  Date = DATEADD(DAY, n.Number, t.TimestampStart)
FROM    @T t
        INNER JOIN Numbers n
            ON n.Number <= DATEDIFF(DAY, t.TimestampStart, t.TimestampStop);

或者，创建您自己的数字表，该表可以反复使用，而无需在每次需要时即时生成。