Sql server MsSQL xml解析为十进制

我正在用这个存储过程处理xml

select
    col.query('./AgreementId').value('.','uniqueidentifier') as [AgreementId],
    x.query('./GrossValue').value('.','decimal(19, 4)') as [GrossValue]
    into #AdvanceInvoices
    from @XML.nodes('/DataFromERP/CustomObjects/Agreements/Agreement') as ref(col)
    cross apply ref.col.nodes('AdvanceInvoices/AdvanceInvoice') as T(x)

问题是GrossValue，它可以为空

<GrossValue></GrossValue>

如何准备它以获得0.0而不是错误

编辑：

我想出了

CAST(COALESCE(NULLIF(ISNULL(x.query('./GrossValue').value('.','nvarchar(50)'),''),''),'0.0') as decimal(19,4)) as [GrossValue],

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但是它非常难看

您可以尝试从元素中获取VARCHAR值，使用to decimal，如果值为NULL，则使用ISNULL获取0.0

ISNULL(TRY_CAST(x.query('./GrossValue').value('.','VARCHAR(20)') AS DECIMAL(19,4)),.0) AS [GrossValue]

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大概和我想象的一样难看。

早在

TRY\u CAST

和

TRY\u CONVERT

发明之前，就有一个

XQuery

CAST:

DECLARE @SomeTable TABLE(ID INT IDENTITY, SomeXML XML);
INSERT INTO @SomeTable VALUES
 (N'<DATA><SomeNumber>1</SomeNumber></DATA>')     --integer
,(N'<DATA><SomeNumber>1.1</SomeNumber></DATA>')   --decimal
,(N'<DATA><SomeNumber></SomeNumber></DATA>')      --empty
,(N'<DATA><SomeNumber>abc</SomeNumber></DATA>')   --invalid
,(N'<DATA><SomeNumber>.123</SomeNumber></DATA>')  --short

SELECT t.SomeXML.value(N'/DATA[1]/SomeNumber[1]/text()[1] cast as xs:decimal?',N'decimal(19,4)')
FROM @SomeTable AS t

或者更简单，只是一个演员：

DECLARE @InvalidNumber VARCHAR(100)='123a'
       ,@ValidNumber VARCHAR(100)='123';

SELECT CAST(@InvalidNumber AS XML).value(N'. cast as xs:int?',N'int') AS InvalidNumber
      ,CAST(@ValidNumber AS XML).value(N'. cast as xs:int?',N'int') AS ValidNumber

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这是可行的，但仅限于SQL Server 2012+（我这边的upvote）我们不得不等待您基于XQuery提出更好的解决方案：）+1

DECLARE @InvalidNumber VARCHAR(100)='123a'
       ,@ValidNumber VARCHAR(100)='123';

SELECT (SELECT @InvalidNumber FOR XML PATH(''),TYPE).value(N'. cast as xs:int?',N'int') AS InvalidNumber
      ,(SELECT @ValidNumber FOR XML PATH(''),TYPE).value(N'. cast as xs:int?',N'int') AS ValidNumber;

DECLARE @InvalidNumber VARCHAR(100)='123a'
       ,@ValidNumber VARCHAR(100)='123';

SELECT CAST(@InvalidNumber AS XML).value(N'. cast as xs:int?',N'int') AS InvalidNumber
      ,CAST(@ValidNumber AS XML).value(N'. cast as xs:int?',N'int') AS ValidNumber