You forgot to initialise @strqry to something other than null. Since it ultimately gets concatenated to everything, the end result is null.
You've got three completely separate queries in there. What are you trying to do?
How about posting what you expect to see from the PRINT statement?
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