獲取每個日期的最新值

Question

我有兩個具有以下結構的表：

DECLARE @Table1 TABLE
(
    IdColumn INT,
    DateColumn DATETIME 
)

DECLARE @Table2 TABLE
(
    IdColumn INT,
    DateColumn DATETIME,
    Value NUMERIC(18,2)
)

我想要做的是從table2中獲取具有在table1中更少或相等日期的最新值。

這是我建立的查詢：

SET NOCOUNT ON

DECLARE @Table1 TABLE
(
    IdColumn INT,
    DateColumn DATETIME 
)

DECLARE @Table2 TABLE
(
    IdColumn INT,
    DateColumn DATETIME,
    Value NUMERIC(18,2)
)


DECLARE @RefDate DATETIME='2012-09-01'
DECLARE @NMonths INT
DECLARE @MonthsCounter INT=1

SELECT @NMonths=DATEDIFF(MM,'2012-09-01','2013-03-01')


WHILE @MonthsCounter<=@NMonths  
BEGIN

    INSERT INTO @Table1
    SELECT 1,@RefDate

    SET @RefDate=DATEADD(MM,1,@RefDate);
    SET @MonthsCounter+=1;

END

INSERT @Table2

SELECT 1,'2012-09-01',1000
UNION
SELECT 1,'2012-12-01',5000
UNION
SELECT 1,'2013-01-01',3000



SELECT
T1.IdColumn,
T1.DateColumn,
T2.Value
FROM @Table1 T1

LEFT JOIN @Table2 T2
ON T2.IdColumn=T1.IdColumn AND T1.DateColumn>=t2.DateColumn

問題是，當一個新值附帶一個較新的日期時，我會獲得到該日期為止的所有值。

IdColumn    DateColumn              Value
----------- ----------------------- ---------------------------------------
1           2012-09-01 00:00:00.000 1000.00
1           2012-10-01 00:00:00.000 1000.00
1           2012-11-01 00:00:00.000 1000.00
1           2012-12-01 00:00:00.000 1000.00
1           2012-12-01 00:00:00.000 5000.00
1           2013-01-01 00:00:00.000 1000.00
1           2013-01-01 00:00:00.000 5000.00
1           2013-01-01 00:00:00.000 3000.00
1           2013-02-01 00:00:00.000 1000.00
1           2013-02-01 00:00:00.000 5000.00
1           2013-02-01 00:00:00.000 3000.00

所需的輸出是以下內容：

IdColumn    DateColumn              Value
----------- ----------------------- ---------------------------------------
1           2012-09-01 00:00:00.000 1000.00
1           2012-10-01 00:00:00.000 1000.00
1           2012-11-01 00:00:00.000 1000.00
1           2012-12-01 00:00:00.000 5000.00
1           2013-01-01 00:00:00.000 3000.00
1           2013-02-01 00:00:00.000 3000.00

我該如何解決？

謝謝。

Answer 1

我只是用正確的語法發布戈登答案：

select t1.*,
       (select top 1 value
        from @table2 t2
        where t2.IdColumn = t1.IdColumn and
              t2.DateColumn <= t1.DateColumn
        order by t2.DateColumn desc
       ) t2value
from @table1 t1

Answer 2

我將與相關子查詢做到這一點：

select t1.*,
       (select top 1 value
        from @table2 t2
        where t2.idColumn = t1.idColumn and
              t2.dateColumn <= t1.dateColumn
        order by t2.dateColumn desc
       ) t2value
from @table1 t1;

Answer 3

評論后，請嘗試以下操作：

INSERT INTO #Table1 (IdColumn, DateColumn)
SELECT IdColumn, DateColumn
FROM #Table2 t
WHERE NOT EXISTS
    (
        SELECT 'X'
        FROM #Table2 tcopy
        where t.IdColumn = tcopy.IdColumn
        and convert(date, t.DateColumn) = convert(date, tcopy.DateColumn)
        and tCopy.DateColumn > t.DateColumn
    )

我使用了“>”，因為您告訴我，表2中沒有具有相同日期/時間的行