SQL Server 2008R2 和创建 XML 文档

Question

第一个 post 在论坛上，因为我真的被这个问题困住了。

以下查询正确地将有效的 XML 文档分配给 @xTempXML 变量（xml 类型）。注：文档的长度（转换为varchar(max) = 711

select @xTempXML = (
        select 
            PrescriberFirstName     as "row/prescriber/name/first",
            PrescriberLastName      as "row/prescriber/name/last",
            PrescriberAddress1      as "row/prescriber/address/line1",
            PrescriberAddress2      as "row/prescriber/address/line2",  
            PrescriberCity          as "row/prescriber/address/city",
            PrescriberState         as "row/prescriber/address/state",
            PrescriberZipCode       as "row/prescriber/address/zipcode",
            PatientFirstName        as "row/patient/name/first",
            PatientLastName         as "row/patient/name/last",
            PatientMiddleName       as "row/patient/name/middle",
            PatientAddress1         as "row/patient/address/line1",
            PatientAddress2         as "row/patient/address/line2", 
            PatientCity             as "row/patient/address/city",
            PatientState            as "row/patient/address/state",
            PatientZipCode          as "row/patient/address/zipcode",
            PatientFileID           as "row/patient/fileid",
            PatientSSN              as "row/patient/ssn",
            PatientDOB              as "row/patient/dob",
            DrugDescription         as "row/medicationprescribed/description",
            DrugStrength            as "row/medicationprescribed/strength",
            DrugDEASchedule         as "row/medicationprescribed/deaschedule",
            DrugQty                 as "row/medicationprescribed/qty",
            DrugDirections          as "row/medicationprescribed/directions",
            DrugFormCode            as "row/medicationprescribed/form",
            DrugDateWritten         as "row/medicationprescribed/writtendate",
            DrugEffectiveDate       as "row/medicationprescribed/effectivedate",
            DrugRefillQty           as "row/medicationprescribed/refill/qty",
            DrugRefillQtyQualifier  as "row/medicationprescribed/refill/qualifier",
            DrugNote                as "row/medicationprescribed/note",
            PharmacyStoreName       as "row/pharmacy/storename",
            PharmacyIdentification  as "row/pharmacy/identification",
            PharmacyAddress1        as "row/pharmacy/address/line1",
            PharmacyAddress2        as "row/pharmacy/address/line2",
            PharmacyCity            as "row/pharmacy/address/city",
            pharmacyState           as "row/pharmacy/address/state",
            pharmacyZipCode         as "row/pharmacy/address/zipcode"
        from 
            Rxarchive
         where ArchiveUUID=@ArchiveRefUUID
           and CreatedDT between @RptParamStartDT and  @RptParamStopDT
           and CHARINDEX(',' + PrescriberFID + ',', ',' + @RptParamFID + ',') > 0 
        FOR XML PATH(''), ROOT('result'), TYPE
        )

declare @sXMLVersion varchar(max) = '<?xml version="1.0" encoding="utf-8"?>'
select len(@sXMLVersion + convert(varchar(max),@xTempXML))

注意：连接字符串的长度 = 749，这是正确的。

set @xFinalXML = convert(xml,(@sXMLVersion + CAST(@xTempXML as varchar(max))))

select LEN(convert(varchar(max),@xFinalXML))

注意：这个变量的长度又回到了711！

select @xFinalXML

变量仍然是有效的XML文档，只是没有版本信息

我做错了什么？

非常感谢任何帮助！

Answer 1

您错过了测试中的一个步骤。试试这个：

SELECT CONVERT(XML, '<?xml version="1.0" encoding="utf-8"?>')

它将return一个空单元格。

根据您的操作（即最终转换为 VARCHAR），没有理由从 XML 数据类型开始。您不妨从 FOR XML 子句中删除 , TYPE，然后连接 @sXMLVersion + @xTempXML

发生这种情况的原因记录在此处：Limitations of the xml Data Type

The XML declaration PI, for example, <?xml version='1.0'?>, is not preserved when storing XML data in an xml data type instance. This is by design. The XML declaration (<?xml ... ?>) and its attributes (version/encoding/stand-alone) are lost after data is converted to type xml. The XML declaration is treated as a directive to the XML parser. The XML data is stored internally as ucs-2. All other PIs in the XML instance are preserved.

此处记录了如何正确处理从 XML 字段/变量中提取数据：XML Best Practices（在 "Text Encoding" 下）

SQL Server 2005 stores XML data in Unicode (UTF-16). XML data retrieved from the server comes out in UTF-16 encoding. If you want a different encoding, you have to perform the required conversion on the retrieved data. Sometimes, the XML data may be in a different encoding. If it is, you have to use care during data loading. For example:

If your text XML is in Unicode (UCS-2, UTF-16), you can assign it to an XML column, variable, or parameter without any problems.

If the encoding is not Unicode and is implicit, because of the source code page, the string code page in the database should be the same as or compatible with the code points that you want to load. If required, use COLLATE. If no such server code page exists, you have to add an explicit XML declaration with the correct encoding.

To use an explicit encoding, use either the varbinary() type, which has no interaction with code pages, or use a string type of the appropriate code page. Then, assign the data to an XML column, variable, or parameter.

Example: Explicitly Specifying an Encoding
Assume that you have an XML document, vcdoc, stored as varchar(max) that does not have an explicit XML declaration. The following statement adds an XML declaration with the encoding "iso8859-1", concatenates the XML document, casts the result to varbinary(max) so that the byte representation is preserved, and then finally casts it to XML. This enables the XML processor to parse the data according to the specified encoding "iso8859-1" and generate the corresponding UTF-16 representation for string values.
SELECT CAST(
    CAST (('<?xml version="1.0" encoding="iso8859-1"?>'+ vcdoc) AS VARBINARY (MAX))
  AS XML)

以下S.O。相关问题：

SQL Server 2008 - Add XML Declaration to XML Output
How to add xml encoding <?xml version="1.0" encoding="UTF-8"?> to xml Output in SQL Server

SQL Server 2008R2 和创建 XML 文档

SQL Server 2008R2 and creating XML document

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