I was in hurry so my code isn't what I'd normally do.  Normally I'd calc only the first/last Monday, then simply subtract/add 7 days to that for other dates.  There's...

The method below is math only, and thus very efficient; works under all date settings; and is flexible/reusable for other days / months / etc..

DECLARE...

You can use APPLY to effectively assign alias names to expressions / results.  You can even nest APPLYs so that the alias from one is used in the next one.

If you want a rolling 60 months:

WHERE OpenDate >= DATEADD(MONTH, DATEDIFF(MONTH, 0, GETDATE()) - 60, 0) /* or -59 if you count the current month...

From the very brief description you've given, it sounds as if:
LocationID
should be the lead clustering key.

If ItemID is unique within LocationID, then the full key should be:

Probably the typical way to do that using a CASE expression would be:

WHERE
1 = CASE @Fruit
  WHEN 'Apples' THEN CASE WHEN...

A loop is just as efficient, or close enough to it, for doing what you want here as any other method would be.

I suppose you avoid a loop...

1) I don't see why READPAST would lead to deadlocking.
2) I would think you do need a transaction to make the READPAST work properly.  You want the first UPDATE lock...

For a temporary "staging" table, where data just waits to be loaded into permanent table(s), no.

But all permanent tables should have at least one candidate key -- i.e....

I have very little time right now, but I want to point out at least a few things.

All tables: Verify the tables are in 2NF and 3NF.

Other...

If you'll (almost) always look up by certain key value(s), and those keys are inherently terrible for clustering (such as a guid), then cluster on all of them.  Yes, in...

My best guess is that it means an error occurred.  By default, a stored proc will return 0 (as the return code).  So that's typically taken as meaning a "good"...

By far the most important thing is to a logical data design before doing a physical one. [You can Google "logical data design" for more details.  A physical design is...

Just adding a clustered index shouldn't slow it down that much, unless perhaps the fillfactor is (way) too low.  Be sure to explicitly specify something like 95+% for the fillfactor...