This should get you what you're looking for...
-- test data from spreadsheet...
IF OBJECT_ID('tempdb..#TestData', 'U') IS NOT NULL
DROP TABLE #TestData;

CREATE TABLE #TestData (
    Record...

Good test Jeff. Thank you for putting that together. Just for the fun of it, I plugged my 1st solution into your harness and it turns out the 1st method...

Entity Framework & LINQ...
recently talked to a company who is looking for a new DBA. As got into the conversation about their environment, it came out that...

Sound like transactions are being opened without being closed. The easy & immediate solution would be to go through and kill all SPIDs that have open transactions, that are suspended...

Itzik touches on the topic in this article... http://sqlmag.com/software-development/puzzle-challenge-graph-matching-t-sql-part-1-concepts

Even simpler still...

SELECT
  YearQ = CONCAT(LEFT(td.OrigDateString, 4), ' Q', DATEPART(QUARTER, od.OrigDate))
FROM
  #TestData td
  CROSS APPLY ( VALUES (CAST(td.OrigDateString + '-01'...

Here's another option...
IF OBJECT_ID('tempdb..#TestData', 'U') IS NOT NULL
DROP TABLE #TestData;

CREATE TABLE #TestData (
    OrigDateString CHAR(7) NOT NULL
    );
INSERT #TestData (OrigDateString) VALUES...

You don't pay interest on interest ever. Unpaid interest and principal balance are kept in two separate buckets and interest is only calculated on the principal.
The only way you'd...

There is no compounding of interest on mortgages (at least not in the U.S.)... That is to say the accrued interest is NOT added to the balance of the loan,...

If I'm going to be using the same set of tools day in and day out, I want the "best" that I can comfortably afford... "Best" doesn't necessarily mean most...