Question

我有一张ExchangeRates表，其中包含countryid和exchangerate，这是有效的：

ExchangeRateID   Country   ToUSD      ExchangeRateDate
1                  Euro     .7400     2/14/2011
2                  JAP      80.1900   2/14/2011
3                  Euro     .7700      7/20/2011

请注意，根据日期，可能会有相同的国家/地区具有不同的费率...例如，2011年2月14日欧元的汇率为.7400，现在是.7700 7/20/2011。

我有另一个订单项表，可根据国家/地区列出项目。在此表格中，每个订单项都有与之关联的日期。订单项日期应根据汇率使用相应的日期和国家/地区。因此，如果我在2011年2月16日有一个国家/地区欧元的订单项，则使用上述数据时，应使用2011年2月14日的欧元值而不是7/20/2011的值，因为日期（条件er。 ExchangeRateDate＆lt; = erli.LineItemDate）。如果我在表中只有一个项目，但是假设我有一个项目日期为8/1/2011那么这个条件（er.ExchangeRateDate＆lt; = erliLineItemDate）将返回多行，因此我的查询将失败。

SELECT     
    er.ExchangeRateID, 
    er.CountryID AS Expr1, 
    er.ExchangeRateDate, 
    er.ToUSD, 
    erli.ExpenseReportLineItemID, 
    erli.ExpenseReportID, 
    erli.LineItemDate
FROM         
    dbo.ExpenseReportLineItem AS erli 
LEFT JOIN
    dbo.ExchangeRate AS er 
ON er.CountryID = erli.CountryID 
AND DATEADD(d, DATEDIFF(d, 0, er.ExchangeRateDate), 0) <= DATEADD(d, DATEDIFF(d, 0, 
                      erli.LineItemDate), 0)
WHERE     (erli.ExpenseReportID = 196)

这个左连接的问题是因为日期是＆lt; =行项目日期所以它返回许多记录，我不得不以某种方式这样做但不知道如何。

LineItem表有多条记录，每条记录都有自己的CountryID：

Item            Country      ParentID    LineItemDate
Line Item 1      Euro           1           2/14/2011
Line Item 2      US             1           2/14/2011
Line Item3       Euro           1           2/15/2011

所以有三条记录为ParentID（ExpenseReportID）= 1.那么我拿这些记录并加入ExchangeRate表，其中我的行项目表中的国家/地区=汇率表的国家/地区（该部分很容易）但是我要做的第二个条件是：

  AND DATEADD(d, DATEDIFF(d, 0, er.ExchangeRateDate), 0) <= DATEADD(d, DATEDIFF(d, 0, 
                          erli.LineItemDate), 0)

但问题出在这里是因为这会从我的汇率表中返回多行，因为欧元被列出两次。

Answer 1

我可能在这里遗漏了一些东西，但据我所知，你的问题的“愚蠢”解决方案是使用A ROW_NUMBER函数和外部过滤器与现有的“返回太多条目”查询（这也可以通过CTE，但对于像这样的简单情况，我更喜欢派生表语法：

SELECT *
FROM (
    SELECT     
        er.ExchangeRateID, 
        er.CountryID AS Expr1, 
        er.ExchangeRateDate, 
        er.ToUSD, 
        erli.ExpenseReportLineItemID, 
        erli.ExpenseReportID, 
        erli.LineItemDate,
        ROW_NUMBER() OVER (PARTITION BY ExpenseReportID, ExpenseReportLineItemID ORDER BY ExchangeRateDate DESC) AS ExchangeRateOrderID
    FROM dbo.ExpenseReportLineItem AS erli 
    LEFT JOIN dbo.ExchangeRate AS er 
        ON er.CountryID = erli.CountryID 
            AND DATEADD(d, DATEDIFF(d, 0, er.ExchangeRateDate), 0) 
                <= DATEADD(d, DATEDIFF(d, 0, erli.LineItemDate), 0)
    WHERE (erli.ExpenseReportID = 196)
        --For reasonable performance, it would be VERY nice to put a filter
        -- on how far back the exchange rates can go here:
        --AND er.ExchangeRateDate > DateAdd(Day, -7, GetDate())
) As FullData
WHERE ExchangeRateOrderID = 1

对不起，如果我误解了，否则希望这有帮助！

Answer 2

如果你可以在你的ExchangeRates表中添加一个名为（类似的东西）的附加列，这会让你的生活变得更轻松

ExchangeRateToDate

单独的流程可以在添加新条目时更新上一个条目。

然后，你可以查询LineItemDate＆gt; = ExhangeRateDate和＆lt; = ExchangeRateToDate

（处理最后一个，可能是一个null的ExchangeRateToDate，作为特例）。

Answer 3

我会创建一个内存表，用ExchangeRateDates From＆amp;创建一个ExchangeRate表。要。
在此之后剩下要做的就是在您的查询中加入此CTE而不是您的ExchangeRate表，并添加条件，其中日期为between日期来自/。

SQL语句

;WITH er AS (
    SELECT  rn = ROW_NUMBER() OVER (PARTITION BY er1.ExchangeRateID ORDER BY er2.ExchangeRateDate DESC)
            , er1.ExchangeRateID
            , er1.Country
            , ExchangeRateDateFrom = ISNULL(DATEADD(d, 1, er2.ExchangeRateDate), 0)
            , ExchangeRateDateTo = er1.ExchangeRateDate
            , er1.ToUSD
    FROM    @ExchangeRate er1
            LEFT OUTER JOIN @ExchangeRate er2
                ON  er1.Country = er2.Country
                    AND er1.ExchangeRateDate >= er2.ExchangeRateDate
                    AND er1.ExchangeRateID > er2.ExchangeRateID     
)
SELECT  er.ExchangeRateID, 
        er.CountryID AS Expr1, 
        er.ExchangeRateDateTo, 
        er.ToUSD, 
        erli.ExpenseReportLineItemID, 
        erli.ExpenseReportID, 
        erli.LineItemDate
FROM    dbo.ExpenseReportLineItem AS erli 
        LEFT JOIN er ON er.CountryID = erli.CountryID 
                        AND DATEADD(d, DATEDIFF(d, 0, er.ExchangeRateDateTo), 0) <= DATEADD(d, DATEDIFF(d, 0, erli.LineItemDate), 0)
                        AND DATEADD(d, DATEDIFF(d, 0, er.ExchangeRateDateFrom), 0) >= DATEADD(d, DATEDIFF(d, 0, erli.LineItemDate), 0)
WHERE   (erli.ExpenseReportID = 196)
        and er.rn = 1

测试脚本

DECLARE @ExchangeRate TABLE (
    ExchangeRateID INTEGER
    , Country VARCHAR(32)
    , ToUSD FLOAT
    , ExchangeRateDate DATETIME
)   

INSERT INTO @ExchangeRate 
VALUES  (1, 'Euro', 0.7400, '02/14/2011')
        , (2, 'JAP', 80.1900, '02/14/2011')
        , (3, 'Euro', 0.7700, '07/20/2011')     
        , (4, 'Euro', 0.7800, '07/25/2011')     

;WITH er AS (
    SELECT  rn = ROW_NUMBER() OVER (PARTITION BY er1.ExchangeRateID ORDER BY er2.ExchangeRateDate DESC)
            , er1.ExchangeRateID
            , er1.Country
            , ExchangeRateDateFrom = ISNULL(DATEADD(d, 1, er2.ExchangeRateDate), 0)
            , ExchangeRateDateTo = er1.ExchangeRateDate
            , ToUSD = er1.ToUSD
    FROM    @ExchangeRate er1
            LEFT OUTER JOIN @ExchangeRate er2
                ON  er1.Country = er2.Country
                    AND er1.ExchangeRateDate >= er2.ExchangeRateDate
                    AND er1.ExchangeRateID > er2.ExchangeRateID     
)
SELECT  *
FROM    er
WHERE   rn = 1

Answer 4

也许您可以尝试使用table expression进入TOP 1，然后加入表格表达式。那有意义吗？希望这可以帮助。

Answer 5

这可以通过使用一个或多个CTE来解决。这个早期的SO问题应该有所需的构建块： How can you use SQL to return values for a specified date or closest date < specified date?

请注意，您必须将此修改为您自己的架构，并过滤掉更接近但未来的结果。我希望这会有所帮助，但如果还不够，那么我相信我可以发布更详细的答案。

Answer 6

您可以将此作为相关子查询使用，该子查询将为您提供一个表格，其中包含给定日期的最新交换值（在评论中指明）：

SELECT * 
FROM er
    INNER JOIN
    (
        SELECT CountryID, MAX(ExchangeRateDate) AS ExchangeRateDate
        FROM er
        WHERE ExchangeRateDate <= '9/1/2011' 
            -- the above is the date you will need to correlate with the main query...
        GROUP BY Country
    ) iq
    ON iq.Country = er.Country AND er.ExchangeRateDate = iq.ExchangeRateDate

因此完整查询应如下所示：

SELECT     
    iq2.ExchangeRateID, 
    iq2.CountryID AS Expr1, 
    iq2.ExchangeRateDate, 
    iq2.ToUSD, 
    erli.ExpenseReportLineItemID, 
    erli.ExpenseReportID, 
    erli.LineItemDate
FROM dbo.ExpenseReportLineItem AS erli 
    LEFT JOIN
    (
        SELECT * 
        FROM ExchangeRate er
            INNER JOIN
            (
                SELECT CountryID, MAX(ExchangeRateDate) AS ExchangeRateDate
                FROM ExchangeRate er
                WHERE ExchangeRateDate <= erli.LineItemDate 
                -- the above is where the correlation occurs...
                GROUP BY Country
            ) iq
            ON iq.Country = er.Country AND er.ExchangeRateDate = iq.ExchangeRateDate
    ) iq2
    ON er.CountryID = erli.CountryID 
        AND DATEADD(d, DATEDIFF(d, 0, iq2.ExchangeRateDate), 0) <= DATEADD(d, DATEDIFF(d, 0, erli.LineItemDate), 0)
    WHERE     (erli.ExpenseReportID = 196)

Answer 7

如果我不误解你想做什么，你可以使用外部申请来获得最新的汇率。

select *
from ExpenseReportLineItem erli
  outer apply (select top 1 *
               from ExchangeRates as er1
               where er1.Country = erli.Country and
                     er1.ExchangeRateDate <= erli.LineItemDate 
               order by er1.ExchangeRateDate desc) as er

艰难的T-SQL加入左边？

7 个答案:

SQL语句

测试脚本