compare cell 2 with cell 1 and show result

Ajaiswal84 

You can use OVER clause and windows function to resolve it.

1. Use OVER and ROWS to get one previous row.
2. Since it has to use aggregate function with OVER clause, and there only one row in window, so it can use either MIN() OR MAX() to get the value of column Snap_Id.
3. NULL value cannot compare with other value, even NULL it self, so before the comparation, use ISNULL() convert NULL to a constaint value that never be used in bussness logic, I choose -1, and you can choose other value base on your logic.
4. Use IIF or CASE compare and output Result.
5. In your sample, the result of first row, you give it NO as value. But I think YES is more reasonable, and the OVER ROWS return YES default. Whatever, you can force it return NO as your wish, I left a commented IIF function, you can use it to get NO for first row.
6. Your sample shown the result of row_num 2 as YES, I guess it must be a mistake.
7. Test table I created is simple than yours, but all key columns are included.

Here is code:

CREATE TABLE #test
(
	[Id] INT,
	[CaseId] INT,
	[User] VARCHAR(10),
	[Snap_Id] INT,
	[row_num] INT
)

INSERT INTO #test
VALUES
 (11, 100, 'Raj', null, 1)
,(22, 100, 'Mike', null, 2)
,(33, 100, 'RJ', 33, 3)
,(44, 100, 'Mike', null, 4)
,(55, 100, 'RJ', 55, 5)
,(55, 100, 'RJ', 55, 6)


SELECT *, 
--IIF( row_num = 1,  --Deal with first row, result should be NO
--	'NO', 
	IIF(MIN(ISNULL(Snap_id, -1)) OVER(ORDER BY row_num ROWS BETWEEN 1 PRECEDING AND 1 PRECEDING) = ISNULL([Snap_Id], -1),  --NULL value can't be compared, so convert it to a value that never used in buss-logic, I use -1 here.
		'NO', 
		'YES'
	)
--)
AS Result 
FROM #test

DROP TABLE IF EXISTS #test