Question

As you know null never equals null in SQL.

Let’s pretend we have a query like this:

declare @LastName varchar(50) = 'Nixon';
select * from Users 
    where LastName = @LastName;

If I want to allow the variable to be null, I do this:

declare @LastName varchar(50) = 'Nixon';
select * from Users 
    where LastName = IsNull(@LastName, LastName);

But what if LastName is null? I must do this:

declare @Null varchar(50) = '!{-[~]-}!'; -- any-ole gibberish

declare @LastName varchar(50) = 'Nixon';
select * from Users 
    where IsNull(LastName, @Null) = Coalesce(@LastName, LastName, @Null);

This works just fine, and I see many similar approaches out there.

But my question is: is this really the best approach? It seems to me that this is a kludge, but I have thought about it a lot and simply cannot come up with anything better.

EDIT but this seems best:

declare @LastName varchar(50) = 'Nixon';
select * from Users 
    where (@LastName is null) or (@LastName = LastName);

Answer 1

Wouldn’t it be simpler to do this?

declare @LastName varchar(50) = 'Nixon';

SELECT * FROM users
  WHERE (@LastName IS NULL) OR (@LastName = LastName);