Paul
This will get you somewhere near where you want to be.  It involves three table scans, so there may be a better alternative from a performance point of view.

I've never heard of a NULL collation.  If you want all columns to have the same collation as the database, why not specify that collation by name in the ALTER...

What do you mean you'll be having millions of records?  There are only three rows in your required result set.  Please show us your xml_path query, and explain in more...

If you use the STUFF function to insert a colon between the hours and minutes and minutes and seconds, you should then be able to convert to datetime.  If that...

Does the one that fails involve a linked server or an OPENROWSET command or something like that?

John

An interesting problem.  I've seen this before, where the same user is a member of more than one group.  I can't remember what the answer is, though!  Does it:
(1)...

Beatrix is right - this could affect your differential backups.  But it won't break your log backup chain.  Now you've come through this unscathed, this would be a good opportunity...

If you're comfortable with the fact that if the subquery runs first and then releases its lock then its results may have changed by the time the main query has...

Why not just have one AD group for each required permission set?  You might find that you have some groups that contain only one member, but that doesn't matter -...

Something like this:
SELECT
     OrderNo
,    Item
,    OrderQty
,    x.OnHand - SUM(OrderQty) OVER (PARTITION BY Item ORDER BY OrderNo ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) AS OnHand

...
WHERE ID = 1234
AND Title = 'Developer'
...

John

Ignacio

Do you have sp_whoisactive on your server?  You can use it to see current activity all at once, without having to query several DMVs.

John