Cannot read contents when XML has 2 wrappers

问题

This code works fine when you remove the <data> wrapper, from the XML and the nodes, but when you add it, like below, i get 0 results.

  -- Declare XML variable
  DECLARE @data XML;

  -- Element-centered XML
  SET @data =
  N'
  <data xmlns="test.xsd">
    <subdata>
      <customer>
        <id>1</id>
        <name>Allied Industries</name>
      </customer>
      <customer>
        <id>2</id>
        <name>Trades International</name>
      </customer>
    </subdata>
  </data>';

  -- Using the query() method
  SELECT T.customer.query('id').value('.', 'INT') AS customer_id,
         T.customer.query('name').value('.', 'VARCHAR(20)') AS customer_name
  FROM @data.nodes('data/subdata/customer') AS T(customer);

But works fine when i do it like this:

  -- Element-centered XML
  SET @data =
  N'
    <subdata>
      <customer>
        <id>1</id>
        <name>Allied Industries</name>
      </customer>
      <customer>
        <id>2</id>
        <name>Trades International</name>
      </customer>
    </subdata>
 ';

  -- Using the query() method
  SELECT T.customer.query('id').value('.', 'INT') AS customer_id,
         T.customer.query('name').value('.', 'VARCHAR(20)') AS customer_name
  FROM @data.nodes('subdata/customer') AS T(customer);

Does anyone know how or why I'm not getting results in the first example, when the <data> parent wrapper is there?

回答1:

The problem has nothing to do with the number of "wrappers" around your XML data. The issue is: your first sample defines an XML namespace (xmlns="test.xsd") on the <data> node, but your query isn't respecting that.

You need to change your query to be something like this:

-- Using the query() method
;WITH XMLNAMESPACES (DEFAULT 'test.xsd')
SELECT 
    T.customer.query('id').value('.', 'INT') AS customer_id,
    T.customer.query('name').value('.', 'VARCHAR(20)') AS customer_name
FROM 
    @data.nodes('data/subdata/customer') AS T(customer);

Then you'll get results....

Without this XML namespace declaration, your query would work just fine - two wrappers or more doesn't matter at all..

来源：https://stackoverflow.com/questions/10375609/cannot-read-contents-when-xml-has-2-wrappers

标签

xml

sql-server-2008

xquery