如何通过SQL Server从XML节点获取值

Question

I've found several pieces of information online about this but I can't get it working for the life of me.

This is the XML I have:

I need to extract the ID & Name value for each node. There are a lot.

I tried to do this but it returns NULL:

select [xml].value('(/Alter/Object/ObjectDefinition/MeasureGroup/Partitions/Partition/ID)[1]', 'varchar(max)')
from test_xml

I understand the above would return only 1 record. My question is, how do I return all records?

Here's the XML text (stripped down version):

<Alter xmlns="http://schemas.microsoft.com/analysisservices/2003/engine" AllowCreate="true" ObjectExpansion="ExpandFull">
  <ObjectDefinition>
    <MeasureGroup xmlns:xsd="http://www.w3.org/2001/XMLSchema">
      <ID>ts_homevideo_sum_20140430_76091ba1-3a51-45bf-a767-f9f3de7eeabe</ID>
      <Name>table_1</Name>
      <StorageMode valuens="ddl200_200">InMemory</StorageMode>
      <ProcessingMode>Regular</ProcessingMode>
      <Partitions>
        <Partition>
          <ID>123</ID>
          <Name>2012</Name>
        </Partition>
        <Partition>
          <ID>456</ID>
          <Name>2013</Name>
        </Partition>
      </Partitions>
    </MeasureGroup>
  </ObjectDefinition>
</Alter>

Answer 1

You need something like this:

DECLARE @MyTable TABLE (ID INT NOT NULL, XmlData XML)

INSERT INTO @MyTable (ID, XmlData)
VALUES (1, '<Alter xmlns="http://schemas.microsoft.com/analysisservices/2003/engine" AllowCreate="true" ObjectExpansion="ExpandFull">
  <ObjectDefinition>
    <MeasureGroup xmlns:xsd="http://www.w3.org/2001/XMLSchema">
      <ID>ts_homevideo_sum_20140430_76091ba1-3a51-45bf-a767-f9f3de7eeabe</ID>
      <Name>table_1</Name>
      <StorageMode valuens="ddl200_200">InMemory</StorageMode>
      <ProcessingMode>Regular</ProcessingMode>
      <Partitions>
        <Partition>
          <ID>123</ID>
          <Name>2012</Name>
        </Partition>
        <Partition>
          <ID>456</ID>
          <Name>2013</Name>
        </Partition>
      </Partitions>
    </MeasureGroup>
  </ObjectDefinition>
</Alter>')

;WITH XMLNAMESPACES(DEFAULT 'http://schemas.microsoft.com/analysisservices/2003/engine')
SELECT 
    tbl.ID,
    MeasureGroupID = xc.value('(ID)[1]', 'varchar(200)'),
    MeasureGroupName = xc.value('(Name)[1]', 'varchar(200)'),
    PartitionID = xp.value('(ID)[1]', 'varchar(200)'),
    PartitionName = xp.value('(Name)[1]', 'varchar(200)')
FROM
    @MyTable tbl
CROSS APPLY
    tbl.XmlData.nodes('/Alter/ObjectDefinition/MeasureGroup') AS XT(XC)
CROSS APPLY
    XC.nodes('Partitions/Partition') AS XT2(XP)
WHERE   
    ID = 1

First of all, you must respect and include the default XML namespace defined in the root of your XML document.

Next, you need to do a nested call to .nodes() to get all <MeasureGroup> and all contained <Partition> nodes, so that you can reach into those XML fragments and extract the ID and Name from them.

This should then result in something like this as output: