Question

I am trying to do something that should be fairly simple but ISNULL isn’t doing what I thought it would.

Basically I have a stored procedure and I am expecting either PARAM1 OR PARAM2 to have a matching value in my table.

SELECT * FROM MyTable WITH (NOLOCK)
        WHERE      
        field1 = ISNULL(@PARAM1 ,field1 )
        AND        
        field2 = @PARAM2

This works fine until I have NULL fields in my row then it excludes those results. Is there a different method that can cater for this?

Answer 1

ISNULL replaces the first value with the second value, so only if your parameter @PARAM1 is NULL does it replace it with PARAM1. I assume you’re not passing in NULL values, so that’s probably not what you want. More likely you just want to say

WHERE
(Field1 = @PARAM1 OR Field1 IS NULL)
AND
Field2 = @Param2

I Suppose you could use ISNULL in this fashion too:

ISNULL(Field1, @PARAM1) = @PARAM1