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使用FOR XML PATH时,如何删除嵌套查询中的冗余命名空间

sql-server-2008 xml sql

Dog Ears · 技术社区 · 14 年前

:我发现此问题引发了一个Microsoft Connect项目 here

使用时 FOR XML PATH WITH XMLNAMESPACES 为了声明一个默认名称空间,我将在用于XML的嵌套查询的任何顶层节点中复制名称空间声明,我在网上偶然发现了一些解决方案,但我并不完全相信。。。

下面是一个完整的例子

/*
drop table t1
drop table t2
*/
create table t1 ( c1 int, c2 varchar(50))
create table t2 ( c1 int, c2 int, c3 varchar(50))
insert t1 values 
(1, 'Mouse'),
(2, 'Chicken'),
(3, 'Snake');
insert t2 values
(1, 1, 'Front Right'),
(2, 1, 'Front Left'),
(3, 1, 'Back Right'),
(4, 1, 'Back Left'),
(5, 2, 'Right'),
(6, 2, 'Left')



;with XmlNamespaces( default 'uri:animal')
select 
    a.c2 as "@species"
    , (select l.c3 as "text()" 
       from t2 l where l.c2 = a.c1 
       for xml path('leg'), type) as "legs"
from t1 a
for xml path('animal'), root('zoo')

最好的解决方案是什么?

5 回复 | 直到 5 年前

8kb 8 年前

DECLARE @Order TABLE (
  OrderID INT, 
  OrderDate DATETIME)

DECLARE @OrderDetail TABLE (
  OrderID INT, 
  ItemID VARCHAR(1), 
  ItemName VARCHAR(50), 
  Qty INT)

INSERT @Order 
VALUES 
(1, '2010-01-01'),
(2, '2010-01-02')

INSERT @OrderDetail 
VALUES 
(1, 'A', 'Drink',  5),
(1, 'B', 'Cup',    2),
(2, 'A', 'Drink',  2),
(2, 'C', 'Straw',  1),
(2, 'D', 'Napkin', 1)

;WITH XMLNAMESPACES('http://test.com/order' AS od) 
SELECT
  OrderID AS "@OrderID",
  (SELECT 
     ItemID AS "@od:ItemID", 
     ItemName AS "data()" 
   FROM @OrderDetail 
   WHERE OrderID = o.OrderID 
   FOR XML PATH ('od.Item'), TYPE)
FROM @Order o 
FOR XML PATH ('od.Order'), TYPE, ROOT('xml')

<xml xmlns:od="http://test.com/order">
  <od.Order OrderID="1">
    <od.Item xmlns:od="http://test.com/order" od:ItemID="A">Drink</od.Item>
    <od.Item xmlns:od="http://test.com/order" od:ItemID="B">Cup</od.Item>
  </od.Order>
  <od.Order OrderID="2">
    <od.Item xmlns:od="http://test.com/order" od:ItemID="A">Drink</od.Item>
    <od.Item xmlns:od="http://test.com/order" od:ItemID="C">Straw</od.Item>
    <od.Item xmlns:od="http://test.com/order" od:ItemID="D">Napkin</od.Item>
  </od.Order>
</xml>

正如您所说,子查询的结果中重复了名称空间。

根据devnetnewsgroup(网站现已关闭)上的对话,这种行为是一种特性,尽管可以选择 vote

我建议的解决办法是回到 FOR XML EXPLICIT

SELECT
  1 AS Tag,
  NULL AS Parent,
  'http://test.com/order' AS [xml!1!xmlns:od],
  NULL AS [od:Order!2],
  NULL AS [od:Order!2!OrderID],
  NULL AS [od:Item!3],
  NULL AS [od:Item!3!ItemID]
UNION ALL
SELECT 
  2 AS Tag,
  1 AS Parent,
  'http://test.com/order' AS [xml!1!xmlns:od],
  NULL AS [od:Order!2],
  OrderID AS [od:Order!2!OrderID],
  NULL AS [od:Item!3],
  NULL [od:Item!3!ItemID]
FROM @Order 
UNION ALL
SELECT
  3 AS Tag,
  2 AS Parent,
  'http://test.com/order' AS [xml!1!xmlns:od],
  NULL AS [od:Order!2],
  o.OrderID AS [od:Order!2!OrderID],
  d.ItemName AS [od:Item!3],
  d.ItemID AS [od:Item!3!ItemID]
FROM @Order o INNER JOIN @OrderDetail d ON o.OrderID = d.OrderID
ORDER BY [od:Order!2!OrderID], [od:Item!3!ItemID]
FOR XML EXPLICIT

看看这些结果:

<xml xmlns:od="http://test.com/order">
  <od:Order OrderID="1">
    <od:Item ItemID="A">Drink</od:Item>
    <od:Item ItemID="B">Cup</od:Item>
  </od:Order>
  <od:Order OrderID="2">
    <od:Item ItemID="A">Drink</od:Item>
    <od:Item ItemID="C">Straw</od:Item>
    <od:Item ItemID="D">Napkin</od:Item>
  </od:Order>
</xml>

Gabrielius 7 年前

经过数小时的绝望和数百次的审判;错误,我提出了下面的解决方案。

我也有同样的问题,当我想要的时候 就一个 xmlns 属性,在节点只有 FOR XML EXPLICIT 光是方法就太麻烦了。所以是的,我想要 FOR XML PATH 在子查询中也可以设置我自己的 xmlns公司 .

8kb的 回答,因为那太好了。为了更好的理解,我对它做了一些调整。代码如下:

DECLARE @Order TABLE (OrderID INT, OrderDate DATETIME)    
DECLARE @OrderDetail TABLE (OrderID INT, ItemID VARCHAR(1), Name VARCHAR(50), Qty INT)    
INSERT @Order VALUES (1, '2010-01-01'), (2, '2010-01-02')    
INSERT @OrderDetail VALUES (1, 'A', 'Drink',  5),
                           (1, 'B', 'Cup',    2),
                           (2, 'A', 'Drink',  2),
                           (2, 'C', 'Straw',  1),
                           (2, 'D', 'Napkin', 1)

-- Your ordinary FOR XML PATH query
DECLARE @xml XML = (SELECT OrderID AS "@OrderID",
                        (SELECT ItemID AS "@ItemID", 
                                Name AS "data()" 
                         FROM @OrderDetail 
                         WHERE OrderID = o.OrderID 
                         FOR XML PATH ('Item'), TYPE)
                    FROM @Order o 
                    FOR XML PATH ('Order'), ROOT('dummyTag'), TYPE)

-- Magic happens here!       
SELECT 1 AS Tag
      ,NULL AS Parent
      ,@xml AS [xml!1!!xmltext]
      ,'http://test.com/order' AS [xml!1!xmlns]
FOR XML EXPLICIT

结果:

<xml xmlns="http://test.com/order">
  <Order OrderID="1">
    <Item ItemID="A">Drink</Item>
    <Item ItemID="B">Cup</Item>
  </Order>
  <Order OrderID="2">
    <Item ItemID="A">Drink</Item>
    <Item ItemID="C">Straw</Item>
    <Item ItemID="D">Napkin</Item>
  </Order>
</xml>

如果您选择 @xml 单独地,您将看到它包含根节点 dummyTag . 我们不需要它,所以我们用 directive xmltext 对于XML显式

,@xml AS [xml!1!!xmltext]

虽然MSDN中的解释听起来更复杂,但实际上它告诉解析器选择目录属于 XML

不知道有多快的查询,但目前我正在放松和喝苏格兰威士忌像一个绅士,而和平地看着代码。。。

Dog Ears 14 年前

我看到的另一种解决方案是添加 XMLNAMESPACES 将xml构建到临时变量后的声明:

declare @xml as xml;
select @xml = (
select 
    a.c2 as "@species"
    , (select l.c3 as "text()" 
       from t2 l where l.c2 = a.c1 
       for xml path('leg'), type) as "legs"
from t1 a
for xml path('animal'))

;with XmlNamespaces( 'uri:animal' as an)
select @xml for xml path('') , root('zoo');

David Claughton 8 年前

在使用xmlpath时,您不能直接手动声明名称空间,这使得这里的问题更加复杂。SQL Server将不允许任何以“xmlns”开头的属性名和任何带有冒号的标记名。

我不必求助于使用相对不友好的XML显式方法,而是先用“隐藏”的名称空间定义和引用生成XML,然后按如下所示进行字符串替换。。。

DECLARE @Order TABLE (
  OrderID INT, 
  OrderDate DATETIME)

DECLARE @OrderDetail TABLE (
  OrderID INT, 
  ItemID VARCHAR(1), 
  ItemName VARCHAR(50), 
  Qty INT)

INSERT @Order 
VALUES 
(1, '2010-01-01'),
(2, '2010-01-02')

INSERT @OrderDetail 
VALUES 
(1, 'A', 'Drink',  5),
(1, 'B', 'Cup',    2),
(2, 'A', 'Drink',  2),
(2, 'C', 'Straw',  1),
(2, 'D', 'Napkin', 1)

declare @xml xml

set @xml = (SELECT
  'http://test.com/order' as "@xxmlns..od",  -- 'Cloaked' namespace def
  (SELECT OrderID AS "@OrderID", 
    (SELECT 
      ItemID AS "@od..ItemID", 
      ItemName AS "data()" 
     FROM @OrderDetail 
     WHERE OrderID = o.OrderID 
     FOR XML PATH ('od..Item'), TYPE)
   FROM @Order o
   FOR XML PATH ('od..Order'), TYPE)
  FOR XML PATH('xml'))

set @xml = cast(replace(replace(cast(@xml as nvarchar(max)), 'xxmlns', 'xmlns'),'..',':') as xml)

select @xml

我使用“xxmlns”作为“xmlns”的隐形版本,用“…”代替“:”。如果可能将“…”作为文本值的一部分,则这可能不适用于您—您可以用其他内容替换它,只要您选择了构成有效XML标识符的内容。

user996758 user996758 13 年前

我对这些解释有点困惑xmlns:animals“手动执行任务: 下面是我编写的一个生成开放图元数据的示例

DECLARE @l_xml as XML;
SELECT @l_xml = 
(
SELECT 'http://ogp.me/ns# fb: http://ogp.me/ns/fb# scanilike: http://ogp.me/ns/fb/scanilike#' as 'xmlns:og',
    (SELECT
        (SELECT 'og:title' as 'property', title as 'content' for xml raw('meta'), TYPE),
        (SELECT 'og:type' as 'property', OpenGraphWebMetadataTypes.name as 'content' for xml raw('meta'), TYPE),
        (SELECT 'og:image' as 'property', image as 'content' for xml raw('meta'), TYPE),
        (SELECT 'og:url' as 'property', url as 'content' for xml raw('meta'), TYPE),
        (SELECT 'og:description' as 'property', description as 'content' for xml raw('meta'), TYPE),
        (SELECT 'og:site_name' as 'property', siteName as 'content' for xml raw('meta'), TYPE),
        (SELECT 'og:appId' as 'property', appId as 'content' for xml raw('meta'), TYPE)
     FROM OpenGraphWebMetaDatas INNER JOIN OpenGraphWebMetadataTypes ON OpenGraphWebMetaDatas.type = OpenGraphWebMetadataTypes.id WHERE THING_KEY = @p_index 
     for xml path('header'), TYPE),
     (SELECT '' as 'body' for xml path(''), TYPE)
     for xml raw('html'), TYPE
)

RETURN @l_xml

返回预期结果

<html xmlns:og="http://ogp.me/ns# fb: http://ogp.me/ns/fb# scanilike: http://ogp.me/ns/fb/scanilike#">
<header>
<meta property="og:title" content="The First object"/>
<meta property="og:type" content="scanilike:tag"/>
<meta property="og:image" content="http://www.mygeolive.com/images/facebook/facebook-logo.jpg"/>
<meta property="og:url" content="http://www.scanilike.com/opengraph?id=1"/>
<meta property="og:description" content="This is the very first object created using the IOThing &amp; ScanILike software. We keep it in file for history purpose. "/>
<meta property="og:site_name" content="http://www.scanilike.com"/>
<meta property="og:appId" content="200270673369521"/>
</header>
<body/>
</html>

希望这能帮助人们在网上搜索类似的问题

AlwaysLearning 5 年前

如果FOR-XML路径真的工作得更干净,那就太好了。使用@table variables重写原始示例:

declare @t1 table (c1 int, c2 varchar(50));
declare @t2 table (c1 int, c2 int, c3 varchar(50));
insert @t1 values 
    (1, 'Mouse'),
    (2, 'Chicken'),
    (3, 'Snake');
insert @t2 values
    (1, 1, 'Front Right'),
    (2, 1, 'Front Left'),
    (3, 1, 'Back Right'),
    (4, 1, 'Back Left'),
    (5, 2, 'Right'),
    (6, 2, 'Left');

;with xmlnamespaces( default 'uri:animal')
select  a.c2 as "@species",
    (
        select  l.c3 as "text()"
        from    @t2 l
        where   l.c2 = a.c1
        for xml path('leg'), type
    ) as "legs"
from @t1 a
for xml path('animal'), root('zoo');

<zoo xmlns="uri:animal">
  <animal species="Mouse">
    <legs>
      <leg xmlns="uri:animal">Front Right</leg>
      <leg xmlns="uri:animal">Front Left</leg>
      <leg xmlns="uri:animal">Back Right</leg>
      <leg xmlns="uri:animal">Back Left</leg>
    </legs>
  </animal>
  <animal species="Chicken">
    <legs>
      <leg xmlns="uri:animal">Right</leg>
      <leg xmlns="uri:animal">Left</leg>
    </legs>
  </animal>
  <animal species="Snake" />
</zoo>

您可以使用具有通配符命名空间匹配(即,*:elementName)的XQuery在命名空间之间迁移元素,如下所示,但对于复杂的XML来说,这可能相当麻烦:

;with xmlnamespaces( default 'http://tempuri.org/this/namespace/is/meaningless' )
select (
    select  a.c2 as "@species",
        (
            select  l.c3 as "text()"
            from    @t2 l
            where   l.c2 = a.c1
            for xml path('leg'), type
        ) as "legs"
    from @t1 a
    for xml path('animal'), root('zoo'), type
).query('declare default element namespace "uri:animal";
<zoo>
{ for $a in *:zoo/*:animal return
    <animal>
    {attribute species {$a/@species}}
    { for $l in $a/*:legs return
        <legs>
        { for $m in $l/*:leg return
            <leg>{ $m/text() }</leg>
        }</legs>
    }</animal>
}</zoo>');

从而产生您想要的结果:

<zoo xmlns="uri:animal">
  <animal species="Mouse">
    <legs>
      <leg>Front Right</leg>
      <leg>Front Left</leg>
      <leg>Back Right</leg>
      <leg>Back Left</leg>
    </legs>
  </animal>
  <animal species="Chicken">
    <legs>
      <leg>Right</leg>
      <leg>Left</leg>
    </legs>
  </animal>
  <animal species="Snake" />
</zoo>