Thanks. There are tons of these little bitty helpful tricks and you will find a good many are covered in Spackle articles by Jeff Moden.
For fast, accurate and documented assistance in answering your questions, please read this article.
Understanding and using APPLY, (I) and (II) Paul White
Hidden RBAR: Triangular Joins / The "Numbers" or "Tally" Table: What it is and how it replaces a loop Jeff Moden