Test: SELECT VS SET + Multi Statement

DECLARE @Test1 int,  @Test2 int, @Test3 int, @TestVar1 int, @TestVar2 int
DECLARE @Loop int, @Start datetime, @CTR int, @TimesToLoop1 int, @TimesToLoop2 int

SET @Test1 = 0
SET @Test2 = 0
SET @Test3 = 0
SET @Loop = 0
SET @TestVar2 = 0
SET @TimesToLoop1 = 10
SET @TimesToLoop2 = 50000
WHILE @Loop < @TimesToLoop1
BEGIN
	SET @Start = CURRENT_TIMESTAMP
	SET @CTR = 0

	/* Testing the performance of SET */
	WHILE @CTR < @TimesToLoop2
	BEGIN
		SET @TestVar1 = 1
		SET @TestVar2 = @TestVar2 - @TestVar1
		SET @CTR = @CTR + 1
	END

	SET @Loop = @Loop + 1
	SET @Test1 = @Test1 + DATEDIFF(ms, @Start, CURRENT_TIMESTAMP)
END

SET @Loop = 0
SET @TestVar2 = 0
WHILE @Loop < @TimesToLoop1
BEGIN
	SELECT @Start = CURRENT_TIMESTAMP
	SELECT @CTR = 0

	/* Testing the performance of SELECT */
	WHILE @CTR < @TimesToLoop2
	BEGIN
		SELECT @TestVar1 = 1
		SELECT @TestVar2 = @TestVar2 - @TestVar1
		SELECT @CTR = @CTR + 1
	END

	SELECT @Loop = @Loop + 1
	SELECT @Test2 = @Test2 + DATEDIFF(ms, @Start, CURRENT_TIMESTAMP)
END

SET @Loop = 0
SET @TestVar2 = 0
WHILE @Loop < @TimesToLoop1
BEGIN
	SELECT @Start = CURRENT_TIMESTAMP, @CTR = 0

	/* Testing the performance of SELECT with multiple variable assignments */
	WHILE @CTR < @TimesToLoop2
	BEGIN
		SELECT @TestVar1 = 1, @TestVar2 = @TestVar2 - @TestVar1, @CTR = @CTR + 1
	END

	SELECT @Loop = @Loop + 1, @Test3 = @Test3 + DATEDIFF(ms, @Start, CURRENT_TIMESTAMP)
END

SELECT 	(@Test1/CAST(@TimesToLoop1 AS decimal(7,2)))/1000.00 AS [SET],
	(@Test2/CAST(@TimesToLoop1 AS decimal(7,2)))/1000.00 AS [SELECT],
	(@Test3/CAST(@TimesToLoop1 AS decimal(7,2)))/1000.00 AS [SELECT with Multiple Assignments]