Are you just adjusting for a Fiscal Year or similar? You could do that with a Calendar table.

Essentially, you're just checking if the Customer has Instore sales and/or Online sales?
Can't you just do that with IF(COUNTROWS(RELATEDTABLE('Sales'))>1,1,0) and put it in the Customer table?  You might need...

SQL Sat Nashville is tomorrow... if you run fast, you could probably squeeze in a session or two.

Did you run the code to create the function? Sounds like you didn't.

Oh, okay. Thanks! I'll have a play with it and see how I make out.

Like this?
https://stackoverflow.com/questions/420741/getting-list-of-tables-and-fields-in-each-in-a-database

 I suppose you could easily find non-matching tables by grouping on column name and getting COUNT = 1?

SQLCompare by RedGate does that, I...

Figured out a small piece of this that was still wrong. I needed to change so that I get the MAX level for each course. Then it makes sense.  (Because...

Here's an example I shamelessly  copied out of Itzik Ben-Gan's T-SQL Querying book:
SELECT custID, orderID, orderDate, val,
    SUM(val) OVER (PARTITION BY custid, YEAR(orderDate)
                    ORDER BY orderDate
                    RANGE...

(sorry for interrupting)
It's possible to do a running total (if you're using 2012 or later...)
See this: https://docs.microsoft.com/en-us/sql/t-sql/functions/sum-transact-sql?view=sql-server-2017

Look for the Cumulative Total.
PARTITION OVER is analogous to...

What if you do something like copy the column names from the first sheet, then loop through the rest of the sheets, and insert a new row above the existing...

Oh wow... MUCH more readable!

I think I get it... Here's a tiny subset of the columns in the Catalog table:
SELECT ItemID
    , c.[Name] as ReportName
FROM dbo.Catalog c
WHERE c.Type =...

What if you insert the data in batches? That would make the transactions smaller, and maybe faster.