Select Stateemt 中动态 SQL 变量的 XQuery [value()] 问题

Question

我尝试使下面的代码动态化，因为页面 'node' 中的 'name' 属性可以有不同的名称。

当我运行下面的代码 returns 错误 'XQuery [value()]: 'value()' 需要单例（或空序列）时，找到类型为 [ 的操作数=34=]'

我觉得我的主要问题是行 'C.value('(/level1/level2/template/page/@name)[sql:variable("@Counter")]','NVARCHAR(MAX)') AS [页面名称]' 我正在尝试使“@counter”变量动态化。

请问有人有解决办法吗？

XML ID 9371

<level1>
  <level2>
    <template width="594" height="500">
      <page Cid="1" name="Test Page Name" colour="-3355393">
        <image Cid="8" x="432" y="8" w="148" h="95" KeyImage="32861" Ratio="y" />
        <formattedText Cid="14" x="9" y="22" w="253" h="38">
          <p>
            <p>
              Text
            </p>
          </p>
        </formattedText>
      </page>
      <page Cid="6" name="Properties">
        <formattedText Cid="7" x="200" y="148" w="208" h="228">
          <p>
            <p>
              <t>Created by </t>
              <t b="b">Joe Bloggs</t>
            </p>
            <p />
            <p>
              <t>Date published 30/05/2017</t>
            </p>
        </formattedText>
      </page>
    </template>
  </level2>
</level1>

SQL 查询的结果

** 呈现结果

Page Name   | Demographics  
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Test Page Name  | <page Cid="1" name="Test Page Name" colour="-3355393"><image Cid="8" x="432" y="8" w="148" h="95" KeyImage="32861" Ratio="y" /><formattedText Cid="14" x="9" y="22" w="253" h="38"><p><p>Text</p></p> </formattedText></page>
Test Page Name  | <page><formattedText Cid="7" x="200" y="148" w="208" h="228"><p><p> <t>Created by </t><t b="b">Joe Bloggs</t></p><p /><p><t>Date published 30/05/2017</t> </p></formattedText></page>

** 期望的结果

Page Name   | Demographics  
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Test Page Name  | <page Cid="1" name="Test Page Name" colour="-3355393"><image Cid="8" x="432" y="8" w="148" h="95" KeyImage="32861" Ratio="y" /><formattedText Cid="14" x="9" y="22" w="253" h="38"><p><p>Text</p></p> </formattedText></page>
Properties  | <page><formattedText Cid="7" x="200" y="148" w="208" h="228"><p><p> <t>Created by </t><t b="b">Joe Bloggs</t></p><p /><p><t>Date published 30/05/2017</t> </p></formattedText></page> 



DECLARE @TableName VARCHAR(40),
 @opxml AS XML,
 @hDoc AS INT,
 @SQL NVARCHAR (MAX)
   


SELECT @opxml = 
a.[filedata]
FROM [database].[dbo].[xmlfile2] a
where  [Id] = 9371

DECLARE @Counter INT 
DECLARE @MaxNo INT 
SET @Counter=1
SET @MaxNo=(SELECT
COUNT(CAST('<page>' +  CAST(C.query('./child::node()') as nvarchar(max)) + '</page>' as xml))
FROM @opxml.nodes('/level1/level2/template/page') AS T(C))

WHILE ( @Counter <= @MaxNo)
BEGIN

SELECT
C.value('(/level1/level2/template/page/@name)[sql:variable("@Counter")]','NVARCHAR(MAX)') AS         
[Page Name],
CAST('<page>' +  CAST(C.query('./child::node()') as nvarchar(max)) + '</page>' as xml) AS     [Page_XML]
, ROW_NUMBER() OVER (ORDER BY t.c)
FROM @opxml.nodes('/level1/level2/template/page') AS T(C)


SET @Counter  = @Counter  + 1
END

Answer 1

我觉得

SELECT
  C.value('@name','NVARCHAR(MAX)') AS [Page Name],
  C.query('<page>{node()}</page>') AS [Page_XML], 
  ROW_NUMBER() OVER (ORDER BY t.c)
FROM @opxml.nodes('/level1/level2/template/page') AS T(C)

可能足以产生所需的结果，而无需 WHILE 循环。

我认为 value()（例如 C.value('(/level1/level2/template/page/@name)[sql:variable("@Counter")]','NVARCHAR(MAX)')）内部的长路径的原始问题是由于 SQL 服务器中 XQuery 的静态类型检查，为了避免它你基本上需要添加另一个谓词以确保类型检查器知道返回单个值，例如C.value('(/level1/level2/template/page/@name)[sql:variable("@Counter")][1]','NVARCHAR(MAX)')

对我来说，代码

DECLARE @opxml AS XML

SET @opxml = N'<level1>
  <level2>
    <template width="594" height="500">
      <page Cid="1" name="Test Page Name" colour="-3355393">
        <image Cid="8" x="432" y="8" w="148" h="95" KeyImage="32861" Ratio="y" />
        <formattedText Cid="14" x="9" y="22" w="253" h="38">
          <p>
            <p>
              Text
            </p>
          </p>
        </formattedText>
      </page>
      <page Cid="6" name="Properties">
        <formattedText Cid="7" x="200" y="148" w="208" h="228">
          <p>
            <p>
              <t>Created by </t>
              <t b="b">Joe Bloggs</t>
            </p>
            <p />
            <p>
              <t>Date published 30/05/2017</t>
            </p>
          </p>
        </formattedText>
      </page>
    </template>
  </level2>
</level1>'

SELECT
  C.value('@name','NVARCHAR(MAX)') AS [Page Name],
  C.query('<page>{node()}</page>') AS [Page_XML], 
  ROW_NUMBER() OVER (ORDER BY t.c)
FROM @opxml.nodes('/level1/level2/template/page') AS T(C)

产生 table

Page Name   Page_XML    (Kein Spaltenname)
Test Page Name  <page><image Cid="8" x="432" y="8" w="148" h="95" KeyImage="32861" Ratio="y" /><formattedText Cid="14" x="9" y="22" w="253" h="38"><p><p>
              Text
            </p></p></formattedText></page> 1
Properties  <page><formattedText Cid="7" x="200" y="148" w="208" h="228"><p><p><t>Created by </t><t b="b">Joe Bloggs</t></p><p /><p><t>Date published 30/05/2017</t></p></p></formattedText></page> 2

所以至少 Page_Name 似乎很容易通过使用例如C.value('@name','NVARCHAR(MAX)') AS [Page Name]

Select Stateemt 中动态 SQL 变量的 XQuery [value()] 问题

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