Concerning that someone who has probably created at least 100 topics on this forum is now asking what ISNULL, MAX and CAST "means".

Firstly, that query is incomplete, there should be a further Right Parenthesis at the end of it. (there's also no FROM clause, but I'm ignoring that).

If we break...

On a totally unrelated note, why has our webdev suddenly decided he wants all of his data unpivoted >_< ARGH.

So the data isn't already in SQL? Do you not use a Pivot table in Excel already then? These are generally pretty quick, and the direction my thought was going...

Do you have to do this in T-SQL? Could you, instead, for example, use Reporting Services or Excel to do your Pivot for you?

T-SQL can Pivot, but you...

In the Paramter properties, in the advanced pane, change Refresh data when the parameter changes to never refresh. You'll have to physically refresh it then.

Is this along the lines of what you're looking for?
DECLARE @Sku VARCHAR(7), @NewPrice DECIMAL(8,2);
--Set your parameter values

UPDATE Product
SET Price = @NewPrice
WHERE SKU...

What information are you trying to get out of the xml? What do you want your output data to look like?

I might being silly here, but what does you're sub query have to do with your outer query? As far as I can tell, every row in the AdminProduct table...