Question

Imagine I have a chunk of initialisation code at the top of a stored procedure with a number of variable assignments:

SET @proc = 'sp_madeupname' SET @magic_number = 42 SET @tomorrows_date = DATEADD(dd, 1, GETDATE()) ... 

Clearly doing all of the above as one SELECT would be faster:

SELECT      @proc = 'sp_madeupname'     ,@magic_number = 42     ,@tomorrows_date = DATEADD(dd, 1, GETDATE()) ... 

But how much faster? Say if this stored procedure was executed as part of a loop, several thousand times, is it going to make any significant difference to the performance?

Answer 1

In this case, SELECT wins, performance-wise, when performing multiple assignments.

Here is some more information about it:

SELECT vs. SET: Optimizing Loops