在 SQL Server 中更新 XML 字符串时的查询优化？

Question

我正在使用如下所示的 XML 字符串。

我必须按如下方式更新 XML 字符串：

• 如果 XML 字符串包含 1000 条或更多记录，则会终止查询
• 如果 XML 字符串包含

我该怎么做？

示例数据

<root xmlns:json="http://james.newtonking.com/projects/json">
  <row json:Array="true" RowNumber="1">
    <Column json:Array="true" Name="Number" Value="1" />
    <Column json:Array="true" Name="HourFrom" Value="13.2" />
    <Column json:Array="true" Name="HourTo" Value="13.3" />
    <Column json:Array="true" Name="Rate" Value="0.895" />
  </row>
  <row json:Array="true" RowNumber="2">
    <Column json:Array="true" Name="Number" Value="1" />
    <Column json:Array="true" Name="HourFrom" Value="13.3" />
    <Column json:Array="true" Name="HourTo" Value="13.4" />
    <Column json:Array="true" Name="Rate" Value="0.907" />
  </row>
</root>

创建临时表

    CREATE TABLE #xmltable(
                           Id INT Identity (1,1)  PRIMARY KEY CLUSTERED,
                           DataValue XML
                          );


    CREATE PRIMARY XML INDEX indexratesheet ON #xmltable
                    (
                      DataValue 
                     ) 

向表格中插入数据

    INSERT INTO (DataValue ) VALUES(TheXMLfromAbove)

更新表格中的 XML 字符串

    DECLARE @i INT 1
    WHILE(@i<=1000)
    BEGIN
         UPDATE #xmltable SET DataValue.modify('insert <Column Name="ValidationComments" Value="{sql:variable("@validationcomments")}"></Column>
                              into (/root/row[@i=sql:variable("@i")])[1]')
   SET @i=@i+1
   END

Answer 1

如果您必须使用 XML 保留它，那么将整个 XML 分解成一个derivedTable 并从头开始重新构建它应该会更快。

试试这个：

CREATE TABLE #xmltable(
                           Id INT Identity (1,1)  PRIMARY KEY CLUSTERED,
                           DataValue XML
                          );


    CREATE PRIMARY XML INDEX indexratesheet ON #xmltable
                    (
                      DataValue 
                     );

--你的测试 XML

    INSERT INTO #xmltable (DataValue ) VALUES(N'<root xmlns:json="http://james.newtonking.com/projects/json">
  <row json:Array="true" RowNumber="1">
    <Column json:Array="true" Name="Number" Value="1" />
    <Column json:Array="true" Name="HourFrom" Value="13.2" />
    <Column json:Array="true" Name="HourTo" Value="13.3" />
    <Column json:Array="true" Name="Rate" Value="0.895" />
  </row>
  <row json:Array="true" RowNumber="2">
    <Column json:Array="true" Name="Number" Value="1" />
    <Column json:Array="true" Name="HourFrom" Value="13.3" />
    <Column json:Array="true" Name="HourTo" Value="13.4" />
    <Column json:Array="true" Name="Rate" Value="0.907" />
  </row>
</root>');

--粉碎它的查询

SELECT r.value(N'@RowNumber','int') AS RowNumber
      ,r.value(N'(Column[@Name="Number"]/@Value)[1]','int') AS Number
      ,r.value(N'(Column[@Name="HourFrom"]/@Value)[1]','decimal(10,4)') AS HourFrom
      ,r.value(N'(Column[@Name="HourTo"]/@Value)[1]','decimal(10,4)') AS HourTo
      ,r.value(N'(Column[@Name="Rate"]/@Value)[1]','decimal(10,4)') AS Rate
INTO #derivedTable
FROM #xmltable AS t
CROSS APPLY t.DataValue.nodes(N'/root/row') AS A(r);

--重建它的查询

WITH XMLNAMESPACES('http://james.newtonking.com/projects/json' AS json)
SELECT 'true' AS [@json:Array]
      ,t.RowNumber AS [@RowNumber]
      ,'true' AS [Column/@json:Array]
      ,'Number' AS [Column/@Name]
      ,t.Number AS [Column/@Value]
      ,''
      ,'true' AS [Column/@json:Array]
      ,'HourFrom' AS [Column/@Name]
      ,t.HourFrom AS [Column/@Value]
      ,''
      ,'true' AS [Column/@json:Array]
      ,'HourTo' AS [Column/@Name]
      ,t.HourTo AS [Column/@Value]
      ,''
      ,'true' AS [Column/@json:Array]
      ,'Rate' AS [Column/@Name]
      ,t.Rate AS [Column/@Value]

      ,''
      ,'ValidationComments' AS [Column/@Name]
      ,'SomeValue' AS [Column/@Value]
FROM #derivedTable AS t
FOR XML PATH('row'),ROOT('root');

--清理（注意真实数据！）

GO

DROP TABLE #derivedTable;
DROP TABLE #xmltable

这是结果

<root xmlns:json="http://james.newtonking.com/projects/json">
  <row json:Array="true" RowNumber="1">
    <Column json:Array="true" Name="Number" Value="1" />
    <Column json:Array="true" Name="HourFrom" Value="13.2000" />
    <Column json:Array="true" Name="HourTo" Value="13.3000" />
    <Column json:Array="true" Name="Rate" Value="0.8950" />
    <Column Name="ValidationComments" Value="SomeValue" />
  </row>
  <row json:Array="true" RowNumber="2">
    <Column json:Array="true" Name="Number" Value="1" />
    <Column json:Array="true" Name="HourFrom" Value="13.3000" />
    <Column json:Array="true" Name="HourTo" Value="13.4000" />
    <Column json:Array="true" Name="Rate" Value="0.9070" />
    <Column Name="ValidationComments" Value="SomeValue" />
  </row>
</root>

更新

试试这个查询，它适用于所有不同的列列表，但它会重复命名空间声明。这没有错，但很烦人。目前我没有时间考虑黑客攻击。让我知道，如果这对你有用。

WITH XMLNAMESPACES('http://james.newtonking.com/projects/json' AS json)
,CTE AS
(
    SELECT r.value(N'@RowNumber','int') AS RowNumber
          ,r.query('./*') AS TheContent
    FROM #xmltable AS t
    CROSS APPLY t.DataValue.nodes(N'/root/row') AS A(r)
)
SELECT CTE.TheContent AS [*]
      ,'ValidationComments' AS [Column/@Name]
      ,'SomeValue' AS [Column/@Value]
FROM CTE
FOR XML PATH('row'),ROOT('root')