微软认证考试70-461 Work with Data 数据处理 --27%比重--（5.3）
附注：微软认证考试70-461范围[*]Create Database Objects创建数据库对象 (24%)
[*]Work with Data数据处理 (27%)
[*]Modify Data数据修改 (24%)
[*]Troubleshoot & Optimize故障排解及SQL优化 (25%)
本文是第二节Work with Data 数据处理 。第一部分直通车第二部分直通车第三部分直通车第四部分直通车第五部分：Query and manage XML data. May include but not limited to: understand xml datatypes and their schemas and interop w/, limitations & restrictions; implement XML schemas and handling of XML data; XML data: how to handle it in SQL Server and when and when not to use it, including XML namespaces; import and export xml; xml indexing. XML数据的查询与管理。可能包含但不仅限于：理解XML类型，架构，交互，局限性和约束性；实现XML架构和XML数据的处理；了解什么时候使用XML比较恰当，包括XML命名空间；导入导出XML；XML索引。FOX XML指定EXPLICIT
FOR XML 模式可以是 RAW、AUTO、EXPLICIT 或 PATH。它确定产生的 XML 的形状。基本语法：[ FOR { BROWSE | <XML> } ]
<XML> ::=
XML
{
{ RAW [ ('ElementName') ] | AUTO }
[
<CommonDirectives>
[ , { XMLDATA | XMLSCHEMA [ ('TargetNameSpaceURI') ]} ]
[ , ELEMENTS [ XSINIL | ABSENT ]
| EXPLICIT
[
<CommonDirectives>
[ , XMLDATA ]
| PATH [ ('ElementName') ]
[
<CommonDirectives>
[ , ELEMENTS [ XSINIL | ABSENT ] ]
}
<CommonDirectives> ::=
[ , BINARY BASE64 ]
[ , TYPE ]
[ , ROOT [ ('RootName') ] ]
FOX XML指定EXPLICIT一个简单的EXPLICIT例子：with TestXmlExplicit
as
(
select 1 as tag,null as parent,'衣服' as ,null as ,null as
union all
select 2,1,null,'女装',null
union all
select 3,2,null,null,'上衣'
union all
select 3,2,null,null,'裤子'
)
select * from TestXmlExplicit
结果：tag parentclothes!1!categorysubcategory!2!namesubsubcategory!3!name
1 NULL衣服 NULL NULL
2 1 NULL 女装 NULL
3 2 NULL NULL 上衣
3 2 NULL NULL 裤子
执行FOR XML EXPLICIT结果(就是上述SQL后添加FOR XML EXPLICIT)：<clothes category="衣服">
<subcategory name="女装">
<subsubcategory name="上衣" />
<subsubcategory name="裤子" />
</subcategory>
</clothes>
分析FOR XML EXPLICIT：TAG和PARENT列是必须的。PARENT为NULL或0的是根目录。列名上叹号间的数字对应TAG。拿三级目录来说，在一级和二级目录对应列上设为NULL值即可，因为三级目灵只关心三级目录列就行了。如TAG为3的两行，clothes!1!category和subcategory!2!name没有对应值。任意指定同级目录TAG数字不代表目录级别！下面是新同级目录的例子：
with TestXmlExplicit
as
(
select 1 as tag,null as parent,'衣服' as ,null as ,null as ,null as
union all
select 2,1,null,'女装',null,null
union all
select 3,2,null,null,'上衣',null
union all
select 4,2,null,null,null,'裤子'
)
select * from TestXmlExplicit for xml explicit
结果：
<clothes category="衣服">
<subcategory name="女装">
<subsubcategory name="上衣" />
<newcategoryname name="裤子" />
</subcategory>
</clothes>
可以看出，三级目录中的元素名称已经更改成newcategoryname 。
为所有目录添加新属性现在给每级目录添加属性ID，新SQL语句如下：with TestXmlExplicit
as
(
select 1 as tag,null as parent,'衣服' as ,1111 as ,null as ,null as ,null as ,null as
union all
select 2,1,null,null,'女装',2222,null,0
union all
select 3,2,null,null,null,0,'上衣',3331
union all
select 3,2,null,null,null,0,'裤子',3332
)
select * from TestXmlExplicit结果：tag parentclothes!1!categoryclothes!1!idsubcategory!2!namesubcategory!2!idsubsubcategory!3!namesubsubcategory!3!id
1 NULL衣服 1111 NULL NULL NULL NULL
2 1 NULL NULL 女装 2222 NULL 0
3 2 NULL NULL NULL 0 上衣 3331
3 2 NULL NULL NULL 0 裤子 3332
运行FOR XML EXPLICIT，结果：<clothes category="衣服" id="1111">
<subcategory name="女装" id="2222">
<subsubcategory name="上衣" id="3331" />
<subsubcategory name="裤子" id="3332" />
</subcategory>
</clothes>
指定ELEMENTwith TestXmlExplicit
as
(
select 1 as tag,null as parent,'衣服' as ,1111 as ,null as ,null as ,null as !element],null as !element]
union all
select 2,1,null,null,'女装',2222,null,0
union all
select 3,2,null,null,null,0,'上衣',3331
union all
select 3,2,null,null,null,0,'裤子',3332
)
select * from TestXmlExplicit for xml explicit
红色字体部分指定了element，结果：
<clothes category="衣服" id="1111">
<subcategory name="女装" id="2222">
<subsubcategory>
<name>上衣</name>
<id>3331</id>
</subsubcategory>
<subsubcategory>
<name>裤子</name>
<id>3332</id>
</subsubcategory>
</subcategory>
</clothes>
指定ELEMENTXSINILwith TestXmlExplicit
as
(
select 1 as tag,null as parent,'衣服' as ,1111 as ,null as ,null as ,null as ,null as !ELEMENTXSINIL]
union all
select 2,1,null,null,'女装',2222,null,0
union all
select 3,2,null,null,null,0,'上衣',3331
union all
select 3,2,null,null,null,0,'裤子',null
)
select * from TestXmlExplicit for xml explicit
注意红色字体部分，最后一列指定了ELEMENTXSINIL，为了测试，把最后一行最后一列的值改为NULL。
结果：
<clothes xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" category="衣服" id="1111">
<subcategory name="女装" id="2222">
<subsubcategory>
<name>上衣</name>
<id>3331</id>
</subsubcategory>
<subsubcategory>
<name>裤子</name>
<id xsi:nil="true" />
</subsubcategory>
</subcategory>
</clothes>
指定 ID 和 IDREF with TestXmlExplicit
as
(
select 1 as tag,null as parent,N'乐可乐可的部落格' as ,'011' as !id],'099' as !idref]
)
select * from TestXmlExplicit for xml explicit,xmldata
红色字体为XML指定了ID和IDREF类型，通XMLDATA查看架构可知：
<Schema name="Schema6" xmlns="urn:schemas-microsoft-com:xml-data" xmlns:dt="urn:schemas-microsoft-com:datatypes">
<ElementType name="clothes" content="mixed" model="open">
<AttributeType name="category" dt:type="string" />
<AttributeType name="cloid" dt:type="id" />
<AttributeType name="cloidref" dt:type="idref" />
<attribute type="category" />
<attribute type="cloid" />
<attribute type="cloidref" />
</ElementType>
</Schema>
<clothes xmlns="x-schema:#Schema6" category="乐可乐可的部落格" cloid="011" cloidref="099" />
指定 IDREFS 指令with TestXmlExplicit
as
(
select 1 as tag,0 as parent,null as
union all
select 1,0,'022'
union all
select 1,0,'025'
)
select * from TestXmlExplicit for xml explicit,xmldata
结果：
<Schema name="Schema4" xmlns="urn:schemas-microsoft-com:xml-data" xmlns:dt="urn:schemas-microsoft-com:datatypes">
<ElementType name="clothes" content="mixed" model="open">
<AttributeType name="cloidlist" dt:type="idrefs" />
<attribute type="cloidlist" />
</ElementType>
</Schema>
<clothes xmlns="x-schema:#Schema4" cloidlist="022 025"></clothes>
示例中cloidlist的类型是idrefs。IDREFS类型的元素也有多个值。因此，必须使用单独的 SELECT 子句来重复使用相同的标记、父级和键列信息。然后，ORDER BY 必须确保组成IDREFS 值的行的序列成组显示在它们的父元素下。
指定 HIDE HIDE顾名思义，隐藏信息。
with TestXmlExplicit
as
(
select 1 as tag,null as parent,N'衣服' as ,null as ,null as !hide]
union all
select 2,1,null,N'女装',null
union all
select 3,2,null,null,N'上衣'
union all
select 3,2,null,null,N'裤子'
)
select * from TestXmlExplicit for xml explicit
三级目录的subsubcategory!3!name不会显示在结果中，但是HIDE的列可以用来排序。
结果：
<clothes category="衣服">
<subcategory name="女装">
<subsubcategory />
<subsubcategory />
</subcategory>
</clothes>
指定ELEMENT和XML的不同指定ELEMENT会实体化数据即对特殊字符进行转义，XML则不会。
with TestXmlExplicit
as
(
select 1 as tag,null as parent,N'衣服' as ,null as !element],null as !xml]
union all
select 2,1,null,N'<b>女装</b>',N'<b>男装</b>'
)
select * from TestXmlExplicit for xml explicit
结果:
<clothes category="衣服">
<subcategory>
<name><b>女装</b></name>
<name2>
<b>男装</b>
</name2>
</subcategory>
</clothes>
指定CDATAwith TestXmlExplicit
as
(
select 1 as tag,null as parent,N'衣服' as ,null as
union all
select 2,1,null,N'<b>女装</b>'
)
select * from TestXmlExplicit for xml explicit
结果：
<clothes category="衣服">
<subcategory>
<name><!]></name>
</subcategory>
</clothes>
指定XMLTEXTwith TestXmlExplicit
as
(
select 1 as tag,null as parent,N'衣服' as ,null as ,null as
union all
select 2,1,null,N'女装',N'<s NAME="test" id="12">女装补充</s>'
)
select * from TestXmlExplicit for xml explicit
结果：
<clothes category="衣服">
<subcategory NAME="女装" id="12">女装补充</subcategory>
</clothes>
[*]因为对于红色字体 列没有指定 AttributeName，而指定了xmltext 指令，所以 <s>元素中的属性被追加到包含它的 <subcategory> 元素(即subcategory!2!NAME，不是clothes!1!category)的属性列表中。
[*]因为 <xmltext> 元素中的 NAME属性与相同元素级上检索到的 NAME 属性冲突，所以忽略 <xmltext> 元素中的此属性，即使 NAME 为 NULL 也是如此。通常情况下，属性将覆盖溢出中具有相同名称的属性。但是id属性没有冲突，所以保留。
再看另一种情况：
with TestXmlExplicit
as
(
select 1 as tag,null as parent,N'衣服' as ,null as ,null as
union all
select 2,1,null,N'女装',N'<s NAME="test" id="12"><name>子元素</name></s>'
)
select * from TestXmlExplicit for xml explicit
XMLTEXT列值包含了子元素name, 因此当前元素追加到<subcategory>，<name>子元素</name>则作为子元素追加到<subcategory>，结果：
<clothes category="衣服">
<subcategory NAME="女装" id="12">
<name>子元素</name>
</subcategory>
</clothes>
再看：
with TestXmlExplicit
as
(
select 1 as tag,null as parent,N'衣服' as ,null as ,null as !subname!XMLTEXT]
union all
select 2,1,null,N'女装',N'<s NAME="test" id="12"><name>子元素</name></s>'
)
select * from TestXmlExplicit for xml explicit
如果为XMLTEXT指定AttributeName(如subname)，则<s>的属性追加到<subname>，然后作为子元素追加到<subcategory>，结果：
<clothes category="衣服">
<subcategory NAME="女装">
<subname NAME="test" id="12">
<name>子元素</name>
</subname>
</subcategory>
</clothes>
真是 收益 匪浅 真是 收益 匪浅 路边的野花不要，踩。 不错不错，楼主您辛苦了。。。 学习了，谢谢分享、、、 帮你顶下哈！！
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