T-SQL 查询XML

我们经常在SQL Server列中存一些XML来作为配置文件或者是保存特殊信息，那么如何将其展开并查询它或将其呈现为关系数据？ 其实在T-SQL 下可以很容易的实现。

示例xml

<catalog>
     <book id="bk101">
          <author>Gambardella, Matthew</author>
          <title>XML Developer's Guide</title>
          <genre>Computer</genre>
          <price>44.95</price>
          <publish_date>2000-10-01</publish_date>
     </book>
     <book id="bk102">
          <author>Ralls, Kim</author>
          <title>Midnight Rain</title>
          <genre>Fantasy</genre>
          <price>5.95</price>
          <publish_date>2000-12-16</publish_date>
     </book>
</catalog>

我们先把xml插入到一个临时表中，只有两个字段ConfigName和ConfigXML

create table #config
(
     ConfigName varchar(100),
     ConfigXML xml
)

insert into #config
select 'TestConfig', '<catalog>
     <book id="bk101">
          <author>Gambardella, Matthew</author>
          <title>XML Developer''s Guide</title>
          <genre>Computer</genre>
          <price>44.95</price>
          <publish_date>2000-10-01</publish_date>
     </book>
     <book id="bk102">
          <author>Ralls, Kim</author>
          <title>Midnight Rain</title>
          <genre>Fantasy</genre>
          <price>5.95</price>
          <publish_date>2000-12-16</publish_date>
     </book>
</catalog>'

好的，下面来看一下场景是如何用sql 实现的。

1. 获取所有xml 中各个book的子xml内容，　这种情况出现在为前台系统提供xml片段。

查询语句为

select r.value('@id','varchar(50)') as bookid,
config.r.query('.') as xmlconfig
from #config
cross apply ConfigXML.nodes('/catalog/book') as config(r)
where ConfigName =  'TestConfig'

1. 将各个节点转换为关系数据库表结构

查询语句为

select config.r.value('@id', 'varchar(50)') AS BookID,
        config.r.value('(author/text())[1]', 'varchar(50)') AS author,
       config.r.value('(title/text())[1]', 'varchar(50)') AS title,
        config.r.value('(genre/text())[1]', 'varchar(50)') AS genre,
        config.r.value('(price/text())[1]', 'varchar(50)') AS price,
        config.r.value('(publish_date/text())[1]', 'varchar(50)') AS publish_date
from #config
cross apply ConfigXML.nodes('/catalog/book') as config(r)
where ConfigName =  'TestConfig'

查询 bookid为k101的信息

方式1： 直接在2的结果集中加上一个where条件and config.r.value('@id','varchar(50)') = 'bk101'

select config.r.value('@id', 'varchar(50)') AS BookID,
        config.r.value('(author/text())[1]', 'varchar(50)') AS author,
       config.r.value('(title/text())[1]', 'varchar(50)') AS title,
        config.r.value('(genre/text())[1]', 'varchar(50)') AS genre,
        config.r.value('(price/text())[1]', 'varchar(50)') AS price,
        config.r.value('(publish_date/text())[1]', 'varchar(50)') AS publish_date
from #config
cross apply ConfigXML.nodes('/catalog/book') as config(r)
where ConfigName =  'TestConfig'
and config.r.value('@id','varchar(50)') = 'bk101'

方式2：修改cross apply的xml path

select config.r.value('@id', 'varchar(50)') AS BookID,
        config.r.value('(author/text())[1]', 'varchar(50)') AS author,
       config.r.value('(title/text())[1]', 'varchar(50)') AS title,
        config.r.value('(genre/text())[1]', 'varchar(50)') AS genre,
        config.r.value('(price/text())[1]', 'varchar(50)') AS price,
        config.r.value('(publish_date/text())[1]', 'varchar(50)') AS publish_date
from #config
cross apply ConfigXML.nodes('/catalog/book[@id=''bk101'']') as config(r)
where ConfigName =  'TestConfig'

注：如果我们从sql  server参数里面拼接xpath需要添加sql:variable来表示他是一个sql  server变量而不是xml属性名。

declare @bookid varchar(30) = 'bk101'

select config.r.value('@id', 'varchar(50)') AS BookID,
        config.r.value('(author/text())[1]', 'varchar(50)') AS author,
       config.r.value('(title/text())[1]', 'varchar(50)') AS title,
        config.r.value('(genre/text())[1]', 'varchar(50)') AS genre,
        config.r.value('(price/text())[1]', 'varchar(50)') AS price,
        config.r.value('(publish_date/text())[1]', 'varchar(50)') AS publish_date
from #config
cross apply ConfigXML.nodes('/catalog/book[@id=sql:variable("@bookid")]') as config(r)
where ConfigName =  'TestConfig'

４．　查询每个book  的id和author信息

方式１：　使用第二步结果集

select config.r.value('@id', 'varchar(50)') AS BookID,
        config.r.value('(author/text())[1]', 'varchar(50)') AS author
from #config
cross apply ConfigXML.nodes('/catalog/book') as config(r)
where ConfigName =  'TestConfig'

方式２：

select config.r.value('../@id', 'varchar(50)') AS BookID,
        config.r.value('.', 'varchar(50)') AS author
from #config
cross apply ConfigXML.nodes('/catalog/book/author') as config(r)
where ConfigName =  'TestConfig'