标题必须令人困惑,但我试图做的事情很容易通过一个例子来理解。我有一张这样的桌子:
Code Date_ Ratio
73245 Jan 1 1975 12:00AM 10
73245 Apr 18 2006 12:00AM 4
73245 Dec 26 2007 12:00AM 10
73245 Jan 30 2009 12:00AM 4
73245 Apr 21 2011 12:00AM 2
基本上对于每个证券,它给出了一些比率,当比率开始有效时。这个表将更容易使用,如果不是只有一个开始日期,它有一对开始日期和结束日期,如下所示:
Code StartDate_ EndDate_ Ratio
73245 Jan 1 1975 12:00AM Apr 18 2006 12:00AM 10
73245 Apr 18 2006 12:00AM Dec 26 2007 12:00AM 4
73245 Dec 26 2007 12:00AM Jan 30 2009 12:00AM 10
73245 Jan 30 2009 12:00AM Apr 21 2011 12:00AM 4
73245 Apr 21 2011 12:00AM Dce 31 2049 12:00AM(or some random date in far future) 2
如何使用SQL语句将原始表转换为我想要的表?我对SQL的经验很少,我无法弄清楚如何。
请帮忙!谢谢!
答案 0 :(得分:2)
在SQL Server 2012中:
SELECT code,
date_ AS startDate,
LEAD(date_) OVER (PARTITION BY code ORDER BY date_) AS endDate,
ratio
FROM mytable
在SQL Server 2005和2008中:
WITH q AS
(
SELECT *,
ROW_NUMBER() OVER (PARTITION BY code ORDER BY date_) AS rn
FROM mytable
)
SELECT q1.code, q1.date_ AS startDate, q2.date_ AS endDate, q1.ratio
FROM q q1
LEFT JOIN
q q2
ON q2.code = q1.code
AND q2.rn = q1.rn + 1
答案 1 :(得分:0)
也许也可以使用OUTER APPLY,例如:
SELECT t1.Code, t1.Date_ AS StartDate_, ISNULL(t2.EndDate_, CAST('20491231' AS DATETIME)) AS EndDate_
FROM t1 AS t1o
OUTER APPLY
(
SELECT TOP 1 Date_ AS EndDate_
FROM t1
WHERE t1.Code = t1o.Code AND t1.Date_ > t1o.Date_
ORDER BY t1.Date_ ASC
) AS t2