SQL Server 2008 - Need column names as an attribute

Question

I need to create a T-SQL query in SQL Server 2008 which outputs data as XML. But this is a generic process that queries data with different columns, which could have spaces in the column names. Therefore, I'd like the XML to list the column name as an attribute (spaces aren't allowed in element names).

Given a master table which links to a detail table for child records, I would want the output to look like this:

<master id="123">
   <detail colname="customer">John Smith</detail>
   <detail colname="amount">888.45</detail>
   <detail colname="date">01/01/01</detail>
</master>
<master id="456">
   <detail colname="customer">Suzie Jones</detail>
   <detail colname="amount">1000.25</detail>
   <detail colname="date">05/05/01</detail>
</master>

The columns in the detail record can vary, so I can't hardcode them.

I believe this may be possible using PIVOT command, but that gets really ugly when you don't know structure of data. I feel like there's got to be a way to get a column name to appear as an attribute value!

thanks for any advice.

Answer 1

Using XQuery a set of simple xml rows can be unpivoted into the required format

DECLARE @X xml = '<row id="123" customer="John Smith" amount="888.45" date="01/01/01" />'
                +'<row id="456" customer="Suzie Jones" amount="1000.25" date="05/05/01" />'

SELECT  @X.query
        (
            '
            for     $id in //row/attribute::id
            return  <master id="{ string($id) }">
                        {
                            for $attr in //row[@id=$id]/attribute::*
                            where local-name($attr) != "id"
                            return <detail columnname="{ local-name($attr) }">{ string($attr) }</detail>
                        }
                    </master>
            '
        )

Answer 2

Use the FOR XML clause in T-SQL

more examples here

Update

For the OP: use FOR XML EXPLICIT to explicitly set attribute values from columns.

Other EXPLICIT examples:

http://blogs.technet.com/b/wardpond/archive/2006/09/08/454938.aspx

Answer 3

Is there any way you can use "FOR XML" in your query? This does a lot of the heavy lifting for you.

This page details something very similar to what I think you're after: http://msdn.microsoft.com/en-us/library/ms345137(v=sql.90).aspx

Answer 4

You can create a stored procedure to do that as follows:

if exists (select * from dbo.sysobjects where id = object_id(N'[QueryXML]') and OBJECTPROPERTY(id, N'IsProcedure') = 1)
drop procedure QueryXML
GO
create procedure QueryXML
  @Columns VarChar(1000),
  @Table VarChar(100)
as
begin
  declare @query varchar(1100)

  set @query = 'select (select ' + @Columns + ' from ' + @Table + ' for XML PATH(''columns'')) for XML PATH(''''), ROOT (''SampleXML'')'   

  exec (@query)

end

I tried with these table

create table dummy1(
  ID int not null identity(1,1),
  dummy1 int,
  dummy2 int,
  dummy3 int
)
GO

insert into dummy1 (dummy1,dummy2,dummy3) values(1,2,3)
insert into dummy1 (dummy1,dummy2,dummy3) values(4,5,6)
insert into dummy1 (dummy1,dummy2,dummy3) values(7,8,9)
insert into dummy1 (dummy1,dummy2,dummy3) values(10,11,12)
insert into dummy1 (dummy1,dummy2,dummy3) values(13,14,15)
insert into dummy1 (dummy1,dummy2,dummy3) values(16,17,18)

example:

exec QueryXML @Columns = 'ID, dummy1', @Table = 'dummy1'
exec QueryXML @Columns = 'ID, dummy2,dummy3', @Table = 'dummy1'
exec QueryXML @Columns = 'ID, dummy1,dummy2,dummy3', @Table = 'dummy1'

you can also review: sql-server-simple-example-of-creating-xml-file-using-t-sql