How to compare different values in sql server

Question

I must to check if two values, X and Y are different. If both are null, they must be considered as equal.

The unique way I found is:

select 1 as valu         


        

Answer 1

You could try using NULLIF like this:

WHERE NULLIF(@X,@Y) IS NOT NULL OR NULLIF(@Y,@X) IS NOT NULL

Answer 2

I think you could use COALESCE for that

WHERE coalesce(@X, '') <> coalesce(@Y, '')

What it does it returns an empty string if one of variables is null, so if two variables are null the two empty strings become equal.

Answer 3

You can use ISNULL

WHERE ISNULL(@X,'') <> ISNULL(@Y,'')

Answer 4

I typically use a technique I picked up from here

SELECT 1 AS valuesDifferent
WHERE  EXISTS (SELECT @X
               EXCEPT
               SELECT @Y) 

WHERE EXISTS returns true if the sub query it contains returns a row. This will happen in this case if the two values are distinct. null is treated as a distinct value for the purposes of this operation.