Question

I’ve got a table that looks like this:

CREATE TABLE CustomerXmlData
(CustomerId int,
CustomerData xml)

The CustomerId links to the main customer table and the CustomerData is an xml document that looks like this

<Person>
  <Product>
    <Name>ABC</Name>
    <Value>500</Value>
  </Product>
  <Product>
    <Name>XYZ</Name>
    <Value>600</Value>
  </Product>
</Person>

There are several hundred thousand such rows. In pseudocode, what I want to do is “Find the average Value of Product where Name = ‘XYZ'”.

I know how to get values out based on element attributes or based on having a parent that is unique in the document, but neither of those is any use in this situation. I can’t find anything that will let me locate the Name that I want and then get the value of the next sibling.

I can use FOR XML and create an edge table, but would I then have to loop through that with a cursor? I’m hoping for a more efficient solution.

Answer 1

Try this (edited to filter by Name):

DECLARE @Name VARCHAR(50)
SET @Name = 'XYZ'

SELECT Name, AVG(Value) 
FROM (
SELECT 
    c.value('Name[1]', 'VARCHAR(50)') AS Name
    , c.value('Value[1]', 'DECIMAL') AS Value
FROM CustomerXmlData
CROSS APPLY CustomerData.nodes('//Product[Name = sql:variable("@Name")]') AS t(c)
) T
GROUP BY Name