将属性添加到根节点

Question

Please see the DDL below:

create table #Dataset1 (id int not null identity,firstname varchar(30),surname varchar(30), primary key (id))
insert into #Dataset1 (firstname,surname) values ('Mark','Williams')

And the SQL below:

select firstname,surname 
from #Dataset1 
FOR XML PATH('Dataset1')

Which returns:

<Dataset1>
  <firstname>Mark</firstname>
  <surname>Williams</surname>
</Dataset1>

How can I get the SQL to return:

<Dataset1 URN='1'>
  <firstname>Mark</firstname>
  <surname>Williams</surname>
</Dataset1>

URN=1 will be harcoded into the XML ie not generated from the database.

Answer 1

Try this

SELECT
    id AS [@URN]
    ,firstname
    ,surname
FROM #Dataset1
FOR XML PATH ('Dataset1')

Result

<Dataset1 URN="1">
  <firstname>Mark</firstname>
  <surname>Williams</surname>
</Dataset1>

Answer 2

Your question is not all clear to me (especially your last sentence about hardcoded )...

Here are four different approaches:

If your will be hardcoded, ie not generated from the database means a fix value it should be this

SELECT 1 AS [@URN]
      ,firstname
      ,surname 
FROM #Dataset1 FOR XML PATH('Dataset1');

If you want to add this as attribute to an existing XML you could do this

DECLARE @xml XML=
(
    SELECT firstname
          ,surname 
    FROM #Dataset1 FOR XML PATH('Dataset1'),TYPE
);
SET @xml.modify('insert attribute URN {"1"} into (/Dataset1)[1]');
SELECT @xml;

If this should be added later you might do this on string level (but I would not advise this)

DECLARE @xml XML=
(
    SELECT firstname
          ,surname 
    FROM #Dataset1 FOR XML PATH('Dataset1'),TYPE
);
SET @xml=
CAST
( 
    REPLACE
    (
     CAST(@xml AS NVARCHAR(MAX))                
    ,N'<Dataset1>',N'<Dataset1 URN="1">')
AS XML);
SELECT @xml;

All three will return as

<Dataset1 URN="1">
  <firstname>Mark</firstname>
  <surname>Williams</surname>
</Dataset1>

If your "URN" is a namespace actually

WITH XMLNAMESPACES(DEFAULT 'SomeDefault'
                  ,'SomeOther' AS URN)
SELECT firstname
      ,surname 
FROM #Dataset1 FOR XML PATH('Dataset1')

The result would be this

<Dataset1 xmlns:URN="SomeOther" xmlns="SomeDefault">
  <firstname>Mark</firstname>
  <surname>Williams</surname>
</Dataset1>