XML与SQL SERVER2005 (四)

最新推荐文章于 2023-10-06 15:56:01 发布

最新推荐文章于 2023-10-06 15:56:01 发布 · 57 阅读

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#XML #SQL #F# #Blog

本文详细介绍XPath中的路径表达式步骤，包括轴步骤和节点测试的概念。通过具体示例讲解了如何使用child、descendant、parent等轴进行节点查询，并解释了节点测试的作用。

第四篇旨在对路径表达式中的步骤(轴步骤、一般步骤)详细说明。

-- 本文来自happyflystone -优快云博客，

-- 转载请标明出处：http://blog.youkuaiyun.com/happyflystone

------------------------------------------------------------------------

1、先说说轴

轴定义移动的方向，从上下文节点开始，导航到在轴指定的方向上可访问的那些节点。用轴步骤得用到上面一节说的全文、缩写语法及绝对、相对路径。此外假设你对此已经有了解。

下面我们介绍一下2005下的XML支持哪些轴：

Axis 说明

child 返回上下文节点的子级

descendant 返回上下文节点的所有后代

parent 返回上下文节点的父级

attribute 返回上下文节点的属性

self 返回上下文节点本身

descendant-or-self 返回上下文节点及其所有后代

很显然，我们可以想像一下这些轴里除了parent 轴是向反方向的，其它全是正向，所以我们又称除了parent以外的轴是正向轴，而parent 轴是反向轴，其实我们简单点理解一下就是一个是正向向下搜索，一个是反向向上搜索。

好，下面还是以例子来说明问题：

A、下面演示用child轴操作一下查询(注意下面查询语句包括了绝对与相对路径表达式)

declare @xml xml

set @xml = '<address>

<exam>

<name> flystone1 </name>

<street> 1401 Main Street </street>

<city state="NC">Anytown</city>

<postal-code> 210000 </postal-code>

</exam>

<exam>

<name> flystone2 </name>

<street> 1402 Main Street </street>

<city state="NM">Anytown</city>

<postal-code> 210000 </postal-code>

</exam>

</address>

select @xml.query('/child::address/child::exam')

select @xml.query('//exam')

select @xml.query('/address/exam')

select @xml.query('address/exam')

select @xml.query('child::address/child::exam')

--------------------------------------------------------------------

<exam><name> flystone1 </name><street> 1401 Main Street </street><city state="NC">Anytown</city><postal-code> 210000 </postal-code></exam><exam><name> flystone2 </name><street> 1402 Main Street </street><city state="NM">Anytown</city><postal-code>

(1 行受影响)

B、下面看看descendant轴、descendant-or-self轴，其实后者只是比前多了上下文节点，大家看看例子就知道

declare @xml xml

set @xml = '<address>

<exam>

<name>

<lastname>stone1</lastname>

</name>

<street> 1401 Main Street </street>

<city state="NC">Anytown</city>

<postal-code> 210000 </postal-code>

</exam>

<exam>

<name>

<lastname>stone2</lastname>

</name>

<street> 1402 Main Street </street>

<city state="NM">Anytown</city>

<postal-code> 210000 </postal-code>

</exam>

</address>

select @xml.query('/child::address/child::exam/child::name/descendant::*')

select @xml.query('//./address/exam/name/descendant::*')

select @xml.query('/./address/exam/name/descendant::*')

select @xml.query('./address/exam/name/descendant::*')

select @xml.query('/address/exam/name/descendant::*')

select @xml.query('address/exam/name/descendant::*')

-----------------------------------------

<firstname>fly</firstname><lastname>stone1</lastname><firstname>fly</firstname><lastname>stone2</lastname>

(1 行受影响)

declare @xml xml

set @xml = '<address>

<exam>

<name>

<lastname>stone1</lastname>

</name>

<street> 1401 Main Street </street>

<city state="NC">Anytown</city>

<postal-code> 210000 </postal-code>

</exam>

<exam>

<name>

<lastname>stone2</lastname>

</name>

<street> 1402 Main Street </street>

<city state="NM">Anytown</city>

<postal-code> 210000 </postal-code>

</exam>

</address>

select @xml.query('/child::address/child::exam/child::name/descendant-or-self::*')

select @xml.query('//./address/exam/name/descendant-or-self::*')

select @xml.query('/./address/exam/name/descendant-or-self::*')

select @xml.query('./address/exam/name/descendant-or-self::*')

select @xml.query('/address/exam/name/descendant-or-self::*')

select @xml.query('address/exam/name/descendant-or-self::*')

------------------------------------------------------------

<name><firstname>fly</firstname><lastname>stone1</lastname></name><firstname>fly</firstname><lastname>stone1</lastname><name><firstname>fly</firstname><lastname>stone2</lastname></name><firstname>fly</firstname><lastname>stone2</lastname>

(1 行受影响)

C、下面看看parent轴的用法：
declare @xml xml

set @xml = '<address>

<exam>

<name>

<lastname>stone1</lastname>

</name>

<street> 1401 Main Street </street>

<city state="NC">Anytown</city>

<postal-code> 210000 </postal-code>

</exam>

<exam>

<name>

<lastname>stone2</lastname>

</name>

<street> 1402 Main Street </street>

<city state="NM">Anytown</city>

<postal-code> 210000 </postal-code>

</exam>

</address>

select @xml.query('/child::address/child::exam/child::name/parent::exam')

select @xml.query('//name/parent::exam')

--先把上下文定位到name节点然后再找父节点

------------------------------------------------------------------

<exam><name><firstname>fly</firstname><lastname>stone1</lastname></name><street> 1401 Main Street </street><city state="NC">Anytown</city><postal-code> 210000 </postal-code></exam><exam><name><firstname>fly</firstname><lastname>stone2</lastname></name><street> 1402 Main Street </street><city state="NM">Anytown</city><postal-code> 210000 </postal-code></exam>

(1 行受影响)

在SQL　SERVER2005看到一个有意思的东东，我们来试试（里面涉及FLWOR 语句大家先跳过，以后我们再细说FLWOR）

declare @xml xml

set @xml = '

<name>

<lastname>stone1</lastname>

</name>

<street> 1401 Main Street </street>

<city state="NC">Anytown</city>

<postal-code> 210000 </postal-code>

</exam>

<name>