Debug a complex T-SQL procedure on SQL Server

Question

I have a very complex T-SQL procedure about 2000 lines (I didn't develop it). I was asked to fix some bugs on it. I tried some methods as:

• using of debug option that I found in SQL Server Management Studio
• using of "PRINT" statement to watch the variables

My question:
What's the best method to debug a procedure like this?

Answer 1

Start by refactoring the procedure into multiple smaller procedures that can be tested and debugged in isolation.