Dan Field Dan Field - 13 days ago 8
SQL Question

SQL Server FOR XML Path make repeating nodes

I'd like to generate the following output using SQL Server 2012:

<parent>
<item>1</item>
<item>2</item>
<item>3</item>
</parent>


From three different columns in the same table (we'll call them col1, col2, and col3).

I'm trying to use this query:

SELECT
t.col1 as 'item'
,t.col2 as 'item'
,t.col3 as 'item'
FROM tbl t
FOR XML PATH('parent'), TYPE


But what I get is this:

<parent>
<item>123</item>
</parent>


What am I doing wrong here?

Answer

Add a column with NULL as value to generate a separate item node for each column.

SELECT 
  t.col1 as 'item'
 ,NULL
 ,t.col2 as 'item'
 ,NULL
 ,t.col3 as 'item' 
FROM dbo.tbl as t 
FOR XML PATH('parent'), TYPE;

Result:

<parent>
  <item>1</item>
  <item>2</item>
  <item>3</item>
</parent>

SQL Fiddle

Why does this work?

Columns without a name are inserted as text nodes. In this case the NULL value is inserted as a text node between the item nodes.

If you add actual values instead of NULL you will see what is happening.

SELECT 
  t.col1 as 'item'
 ,'1'
 ,t.col2 as 'item'
 ,'2'
 ,t.col3 as 'item' 
FROM dbo.tbl as t 
FOR XML PATH('parent'), TYPE;

Result:

<parent>
  <item>1</item>1<item>2</item>2<item>3</item></parent>

Another way to specify a column without a name is to use the wildcard character * as a column alias.

Columns with a Name Specified as a Wildcard Character

It is not necessary to use the wildcard in this case because the columns with NULL values don't have a column name but it is useful when you want values from actual columns but you don't want the column name to be a node name.

Comments