Question

我从xml中选择，将属性解析为如下列：

Observable.combineLatest(validEmail, validPw, (b1, b2) -> b1 && b2)
  .subscribe(enableButton -> /* enable button based on bool */);

是否可以直接从declare @xml xml select @xml = xml_Function() SELECT Tab.Col.value('@fieldOne','varchar(20)') AS fieldOne, Tab.Col.value('@fieldTwo','varchar(20)') AS fieldTwo FROM @xml.nodes('/row') Tab(Col)进行选择而不将结果复制到xml_Function变量中？

类似的东西：

@xml

Answer 1

据我所知，您无法直接使用nodes()的XML返回功能，但您可以使用CTE或＆＃34;子选择＆＃34;让它内联：

CREATE FUNCTION dbo.ComeBackAsXML(@XmlText VARCHAR(MAX))
RETURNS XML
AS
BEGIN
    DECLARE @x XML=CAST(@XmlText AS XML);
    RETURN @x;
END
GO 

DECLARE @xText VARCHAR(MAX)=
'<root>
  <item id="3">
    <a attr="test1" />
    <a attr="test2" />
    <a attr="test3" />
  </item>
  <item id="5">
    <a attr="test1" />
    <a attr="test2" />
  </item>
</root>';
WITH GetXml AS (SELECT dbo.ComeBackAsXml(@xText) AS AsXml)
SELECT item.value('@id','int') AS ItemID
      ,a.value('@attr','varchar(max)') AS a_Attr
FROM GetXml
CROSS APPLY GetXml.AsXml.nodes('/root/item') AS One(item)
CROSS APPLY One.item.nodes('a') AS The(a);
GO

DROP FUNCTION dbo.ComeBackAsXML;
GO

这是CTE的子选择：

SELECT item.value('@id','int') AS ItemID
      ,a.value('@attr','varchar(max)') AS a_Attr
FROM (SELECT dbo.ComeBackAsXml(@xText)) AS GetXml(AsXml)
CROSS APPLY GetXml.AsXml.nodes('/root/item') AS One(item)
CROSS APPLY One.item.nodes('a') AS The(a);

如果你想让函数可参数化，你必须要知道，你写入XPath表达式的东西 - 几乎在所有情况下 - 都是文字，因此不能参数化......

我认为，你不想要一个通用的通用＆＃34; XML函数处理您可能需要的任何未知结构。我假设有一个给定的XML总是相同的，你只想简短地编写你的查询：

你有几种方法可以去

提供表格并使用WHERE
传入参数并将其与sql:parameter()
动态构建语句（需要存储过程）

在这里，您将找到每种方法的示例：

CREATE FUNCTION dbo.ParseXML(@xml XML)
RETURNS TABLE
AS
RETURN
SELECT item.value('@id','int') AS ItemID
      ,a.value('@attr','varchar(max)') AS a_Attr
FROM @xml.nodes('/root/item') AS One(item)
CROSS APPLY One.item.nodes('a') AS The(a);
GO

DECLARE @x XML=
'<root>
  <item id="3">
    <a attr="test1" />
    <a attr="test2" />
    <a attr="test3" />
  </item>
  <item id="5">
    <a attr="test1" />
    <a attr="test2" />
  </item>
</root>';

SELECT * FROM dbo.ParseXML(@x)
WHERE ItemID=3
GO

ALTER FUNCTION dbo.ParseXML(@xml XML,@ItemID INT)
RETURNS TABLE
AS
RETURN
SELECT item.value('@id','int') AS ItemID
      ,a.value('@attr','varchar(max)') AS a_Attr
FROM @xml.nodes('/root/item[@id=sql:variable("@ItemID")]') AS One(item)
CROSS APPLY One.item.nodes('a') AS The(a);
GO

DECLARE @x XML=
'<root>
  <item id="3">
    <a attr="test1" />
    <a attr="test2" />
    <a attr="test3" />
  </item>
  <item id="5">
    <a attr="test1" />
    <a attr="test2" />
  </item>
</root>';

SELECT * FROM dbo.ParseXML(@x,5);
GO

CREATE PROCEDURE dbo.ParseXMLDynamically(@xml XML,@ItemID INT)
AS
BEGIN
    DECLARE @SqlCmd NVARCHAR(MAX)=
'SELECT item.value(''@id'',''int'') AS ItemID
      ,a.value(''@attr'',''varchar(max)'') AS a_Attr
FROM @xml.nodes(''/root/item[@id=' +  CAST(@ItemID AS VARCHAR(100)) + ']'') AS One(item)
CROSS APPLY One.item.nodes(''a'') AS The(a)';

EXECUTE sp_executesql @SqlCmd,N'@xml XML',@xml;
END
GO

DECLARE @x XML=
'<root>
  <item id="3">
    <a attr="test1" />
    <a attr="test2" />
    <a attr="test3" />
  </item>
  <item id="5">
    <a attr="test1" />
    <a attr="test2" />
  </item>
</root>';

EXEC dbo.ParseXMLDynamically @x, 5;
GO

DROP PROCEDURE dbo.ParseXMLDynamically;
DROP FUNCTION dbo.ParseXML;

直接从用户定义的函数中选择xml节点

1 个答案: