使用来自XML Schema集合的带有XML列的表创建表格时使用Content关键字

Question

在创建具有XML类型列的表时，我指的是一个复杂的 xml架构集合。当我指定 xml schema 时，我可以选择提及 content 或文档关键字。后者将确保XML数据存储为单列中的文档。

根据视频教程 content 将存储在片段中的XML数据。

除了上面的陈述外，我没有找到关于 content 关键字的使用情况的其他地方，并且它对模式和数据含义。

我想知道碎片是如何创建和管理的，以及如何单独查询它们。此外，片段如何相关。接下来，当我修改XML架构集合时，影响是什么。

Answer 1

actually i think SQLServer 2005 XML is quite good documented.
CONTENT is the default and allows any valid XML. DOCUMENT is more specific and means that the XML-Data you can to store is only allowed to have a single Top-Level node.

Create:

CREATE TABLE XmlCatalog ( 
   ID INT PRIMARY KEY, 
   Document XML(CONTENT myCollection))

Insert:

INSERT INTO XmlCatalog VALUES (2, 
'<doc id="123">
    <sections>
   <section num="1"><title>XML Schema</title></section>
   <section num="3"><title>Benefits</title></section>
   <section num="4"><title>Features</title></section>
    </sections>
</doc>')

Select:

SELECT xCol.query('/doc[@id = 123]//section')   
FROM XmlCatalog   
WHERE  xCol.exist ('/doc[@id = 123]') = 1

...and so on. The query language exceeds more or less in a subset of xpath 1.0.

If you amend an XSD it is checked on Inserts and Updates and stored within the xml of each element. As far as i understand the doc it is also allowed to add multiple schemas for one column so that entries can reference to different schemas.

EDIT:
Ok, after reading the specific parts of the documentation i think i understand what your problem is. The reference isn't very clear on that point but as far as i understand it only Entries with one top level node can to be bound to XSD schemas.
Due to the fact that XSD-Schemas require a single top level node defining the used XSD file it won't be possible to validate fragments containing more than one top level element. I haven't tried but i think it can't be done.
However it seems to be valid to define a CONTENT column, amend an XSD and store both, XML with one top level node referencing the XSD as well as XML-fragments which will only checked for wellformedness. The fragments can be accessed using the XPath query language show in the select statement above.
I can't tell you much about performance implications. The reference mentions that XSDs are stored inline so this will need some extra space within the db. The XPath queries need to be executed too. Despite the fact that xpath usually is quite fast i guess it could decrease performace cause it needs to be performed on each row to get the result. To be sure i think you have to check the execution plan for your specific query depending on size and complexity of the stored xml as well as the xpath expression.