INSERT INTO LOCAL_Item VALUES ('64082','Null', 'Ear Defenders')
should be
INSERT INTO LOCAL_Item VALUES ('64082',Null, 'Ear Defenders')
i.e. you can't have quotes around the Null

Thanks Harsha, a great script (5 stars awarded).
This saved me a lot of effort as I had to detach and then reattach about 50 databases on two instances...

1. Make sure all your stored procedures are in source control.
2. For each stored procedure you should have a script like this:
IF OBJECT_ID('dbo.myStoredProcedure','P') IS NULL 
 ...

https://www.mssqltips.com/sqlservertip/2964/encrypting-and-decrypting-sql-server-stored-procedures-views-and-userdefined-functions/

If you want to improve performance on selects (not updates and inserts) you can create the function with schemabinding, then you can persist the column:
ALTER FUNCTION...

Why doesn't it come up with: 
45,27
45,50
45,45
?
Can you provide your cursor solution so we can convert it to a set solution?

You should read this thread: https://www.sqlservercentral.com/Forums/2008959/does-use-of-large-datatypes-where-much-smaller-ones-will-do-affect-performance

You can set up perfmon to monitor CPU usage. for a few days then look at the plot.
If you have enterprise version of SQL Server you can create an...