SQL解析XML列数据

Question

I have very little experience with SQL Server. Here is what I am trying to accomplish:

I have a table with many rows. Every row contains a column named "Config". The data stored in the Config column is of the xml type. The xml structure looks like this:

<root>
 <path1>
  <path2>
   <path3>true</path3>
  </path2>
 </path1>
</root>

I am trying to go through every row in the table and find the percentage of true to false values of <path3> .

I looked at some SQL documentation and tried to use the value() function I am having difficulties extracting the XML data from the column:

select Config.value('(/root/path1/path2/path3)[1]','nvarchar(max)') from [MyDB].[dbo].[MyTable]

Here is the result of my query:

I would like to query and extract data from the XML "Config" column of my table and aggregate that data into columns.

Answer 1

You need to specify namespaces in the query when xml is built with namespaces. For example

CREATE TABLE tbl (Config xml);
INSERT INTO tbl (Config)
VALUES ('<root xmlns="abc">
 <path1>
  <path2>
   <path3>true</path3>
  </path2>
 </path1>
</root>') ;

Then

with xmlnamespaces (DEFAULT 'abc')
select Config.value('(/root/path1/path2/path3)[1]','nvarchar(max)') path3Txt
from tbl;

or explicit specification

with xmlnamespaces ('abc' as x)
select Config.value('(/x:root/x:path1/x:path2/x:path3)[1]','nvarchar(max)') path3Txt
from tbl;

Answer 2

You would need to use CROSS APPLY. Check it out.

SQL

-- DDL and sample data population, start

    DECLARE @tbl TABLE (ID INT IDENTITY(1,1) PRIMARY KEY, [Config] XML);
    INSERT INTO  @tbl
    VALUES (N'<root>
        <path1>
            <path2>
                <path3>true</path3>
            </path2>
        </path1>
    </root>')
    , (N'<root>
        <path1>
            <path2>
                <path3>false</path3>
            </path2>
        </path1>
    </root>');
    -- DDL and sample data population, end

    ;WITH rs AS
    (
       SELECT ID
          , col.value('(./text())[1]','VARCHAR(20)') AS Result
        FROM @tbl tbl
          CROSS APPLY tbl.[Config].nodes('/root/path1/path2/path3') AS tab(col)
    )
    SELECT * FROM rs;