Grouping values under elements FOR XML - sql

Question

I am trying to format the output of a query using FOR XML in SQL Server 2012.
Each PART_NO can have a varying number of SUPPLIER_PART_NUMBER's mapped to it.
The table has data in the following format.
PART_NO SUPPLIER_PART_NO
------- ----------------
AAA 1
AAA 2
BBB 3
BBB 4
BBB 5
The desired output is as follows where part AAA has two supplier part numbers and part BBB has three supplier part numbers, and the supplier part numbers are nested below the part number.
<root>
<item PartNo ="AAA">
<mpn>1</mpn>
<mpn>2</mpn>
</item>
<item PartNo ="BBB">
<mpn>3</mpn>
<mpn>4</mpn>
<mpn>5</mpn>
</item>
</root>
The closest I can get is below, but this does not group the mpn under PartNo:
SELECT
[PART_NO] as 'item/#PartNo',
[SUPPLIER_PART_NO] as 'mpn'
FROM
[dbo].[supplier_part_mapping2]
ORDER BY
PART_NO
FOR XML PATH('') , ROOT('root');
Thank you in advance

Answer 1

Try this:
SELECT
p1.PART_NO as 'item/#PartNo',
(SELECT
SUPPLIER_PART_NO AS 'mpn'
FROM
[dbo].[supplier_part_mapping2] p2
WHERE
p1.PART_NO = p2.PART_NO
FOR XML PATH(''), TYPE) AS 'item'
FROM
[dbo].[supplier_part_mapping2] p1
GROUP BY
PART_NO
ORDER BY
PART_NO
FOR XML PATH('') , ROOT('root');
This should produce:
You basically need to group by the PART_NO so that you get only one <item> entry for each distinct PART_NO, and you need to grab the "sub-elements" as a subquery to list them all together under one parent node.