Question

I’m having a problem with a stored procedure. It’s comparing a new record with an existing one to check for changes. This is done like this:

SELECT 1 FROM Table
WHERE Id= @Id
AND Field1 = @Field1
AND Field2 = @Field2
AND Field3 = @Field3
AND Field4 = @Field4
AND Field5 = @Field5
AND LEDTS IS NULL

This seems to fail when fields are NULL. I know = NULL doesn’t work the way you might expect it to, but I didn’t know it also fails in things like this. When I change the field comparison to things like

(Field1 IS NULL AND Field2 IS NULL) OR Field1 = @Field2

it does work. Is there a better way to do this?

Answer 1

SET ANSI_NULLS can control this behavior… Setting SET ANSI_NULLS OFF will make NULL = NULL evaluate to true.

But I would recommend against actually setting SET ANSI_NULLS OFF, and instead try to limit the fields in the database that are “nullable”.