the upgrade has created some database schema in the back end

Please explain what you mean by this. A new database schema should not do anything bad, per se.

That requirement looks suspect to me.

Do (a) and (b) both have to be true (AND), or is it a case of one or the other (OR)?

One benefit I see is to do with vertical alignment.

SELECT col1
      ,LongCol2
      ,LongerCol3
    ...

My testing agrees with yours ... line 1 appears to be the line just before CREATE PROC

PolicyType is Pascal case, not camel case, which would be policyType.

I guess I'm lucky: I've been reading code without underscores for so long that I find it just as easy...

You would use TINYINT with 1 or 0 so you can do a SUM aggregate.  If you used Y/N, couldn't you get the same result by using some function to...

Not tested, but the syntax will be more like this:

(SafetyBaseline ==  FALSE  && RegulationBaseline ==  FALSE  && EnvironmentSafetyBaseline ==  FALSE  && EnvironmentSecurityBaseline ==  FALSE) ? IsActive = False: IsActive =...

Just to be sure, it wasn't meant as any kind of slam for missing something, Phil.  I absolutely thought it excellent emphasis on a problem that would eat...

Jeff, your advice was so excellent, I clearly didn't bother reading it properly 🙂

What do you mean by this?

T has 57,000 distinct rows

I mean, why did you use the word 'distinct'?

Following on from Jeff's excellent advice, I'd like to add a little more. I'd suggest removing all spaces from your column names ... makes your code much less cumbersome because...

Declaring variables as Varchar without an explicit length is considered bad practice and can lead to unexpected results.

Use VARCHAR(n) (where n is the longest expected length) instead.

And if you're at all OCD with your database object names (or maybe you like to check everything in to source control & therefore avoid random names), consider using extended...

You need to put your defaults in parentheses, eg:

DEFAULT ('Y')

In stored procedure Procedure SP_FlagTests_CY, there is a reference to a column BaseSolvencyBuffer_CYMinus1, and that column cannot be found in the context of the query.

If you show us the content...