WHERE语句不包含空值需要包含空值和失败的匹配

Question

对于下面的代码，where语句的第二部分（after和）将排除d.CreditRating为空的所有内容。该声明需要选择最近的日期并且仅通过c.ISIN，c.SEDOL，c.CUSIP中的一个来匹配。如何使信用评级为空，因为我们无法匹配或实际值为空？

该查询只在运行where语句前的所有内容以及where语句运行时的所有内容，但不会选择最近的日期。谢谢。

Select e.MSPortfolioId, 
     b.PortfolioId, 
     c.DetailHoldingTypeId, 
     d.CreditRating, 
     b.MarketValue, 
     c.SecurityId, 
     c.ISIN, 
     c.SEDOL, 
     c.CUSIP 
From PortfolioCoreData.dbo.LatestPortfolio e 
Left Join HoldingData.dbo.HoldingDetail b 
    On e.LatestStoredPortfolioId = b.PortfolioId 
Left Join HoldingData.dbo.SecurityInfo c 
    On b.SecurityId = c.SecurityId 
Left Join BondData.dbo.BondCreditRating d 
    On (Case When c.CUSIP Is Not Null Then c.CUSIP 
      When c.ISIN Is Not Null Then c.ISIN 
      Else c.SEDOL End) = d.BondId 
Where e.MSPortfolioId In ('5670', '4404', '5973', '861996') 
     And (d.EffectiveDate = (Select Max(d.EffectiveDate) 
            From BondData.dbo.BondCreditRating d 
            Where (Case When c.CUSIP Is Not Null Then c.CUSIP When c.ISIN Is Not Null Then c.ISIN When c.SEDOL Is Not Null Then c.SEDOL End) = d.BondId)); 

Answer 1

发生这种情况是因为您的查询选择只有EffectiveDate值，要添加EffectiveDate为null，您也需要问它。

你可以试试这个地方

Where e.MSPortfolioId In ('5670', '4404', '5973', '861996') 
     And 
     (
     (d.EffectiveDate = (
            Select Max(d.EffectiveDate) 
            From BondData.dbo.BondCreditRating d 
            Where (Case When c.CUSIP Is Not Null Then c.CUSIP 
               When c.ISIN Is Not Null Then c.ISIN 
               When c.SEDOL Is Not Null Then c.SEDOL 
              End 
             ) = d.BondId 
          ) 
      ) OR d.EffectiveDate is null);