How can I get a list of columns from this SQL Server XML field?

I have an xml fragment like the following example and I'd like to get the list of columns out and turn them into a comma-separated list but I'm really struggling to f开发者_运维知识库igure out the syntax for working with the XML data type and the documentation I've found reads like Korean stereo instructions :(

<ROOT>
<DATAVIEW>sp_Demo</DATAVIEW>
<WHERECLAUSE>X=4</WHERECLAUSE>
<COLUMNS>
  <COLUMN>ImageHTML</COLUMN>
  <COLUMN>Task_ID</COLUMN>
</COLUMNS>
</ROOT>

Can anyone point me at a beginners example or give me a pointer on how to do this?

From the XML fragment above I'd like to return a string containing "ImageHTML,Task_ID"

Well it's not pretty but this does the trick, thanks for the pointer Louis.

DECLARE MY_CURSOR Cursor
FOR 
Select  Substring(Substring(CAST(T.Item.query('.') AS varchar(50)),0,LEN(CAST(T.Item.query('.') AS varchar(50)))-8),9,LEN(CAST(T.Item.query('.') AS varchar(50))))
From @Data.nodes('ROOT/COLUMNS/COLUMN') AS T(Item) 

    Open MY_CURSOR
    DECLARE @ColumnName varchar(50)
    DECLARE @RunningTotal varchar(2000)
    SET @RunningTotal=''

    FETCH NEXT FROM MY_CURSOR INTO @ColumnName
    WHILE (@@Fetch_STATUS<>-1)
    BEGIN
    IF (@@FETCH_STATUS<>-2)
    IF LEN(@RunningTotal)>0 SET @RunningTotal=@RunningTotal+','
    SET @RunningTotal=@RunningTotal+@ColumnName

    FETCH NEXT FROM MY_CURSOR INTO @ColumnName
    END
    CLOSE MY_CURSOR
    DEALLOCATE MY_CURSOR

    PRINT @RunningTotal

Final Update: While my cursor version worked, Akash presented a much neater solution below.

You do not need a cursor here. You need two things:

• the xml data type methods .nodes() and .value()
• a well-known trick for producing a comma-separated list from a rowset

Setup:

DECLARE @xml xml

SET @xml = '
<ROOT>
<DATAVIEW>sp_Demo</DATAVIEW>
<WHERECLAUSE>X=4</WHERECLAUSE>
<COLUMNS>
  <COLUMN>ImageHTML</COLUMN>
  <COLUMN>Task_ID</COLUMN>
</COLUMNS>
</ROOT>
'

Output:

DECLARE @output nvarchar(max)

SELECT
    @output = COALESCE(@output + ', ', '') + C.value('text()[1]', 'nvarchar(MAX)')
FROM
    @xml.nodes('//COLUMN') X(C)

SELECT @output

Explanation:

.nodes() performs a shred of xml into rows. In this case, it interrogates the xml with the xpath //COLUMN and produces a rowset with each matching node as a row. This rowset is aliased to a table named X with one column C.

In the SELECT clause, each xml node has its text() value extracted with .value()

The @output trick is a standard method for producing a comma-delimited list.

Output:

ImageHTML, Task_ID

Hopefully these terms and methods will enable you to find the apropriate docs and examples.

Is this of some help ?

http://www.sqlteam.com/forums/topic.asp?TOPIC_ID=61409

enjoy