Change Primary key default value

How can you change the value of a field from default value of 0 to something else.

Adobe Campaign counts empty columns as 'null':

...so we are placing a filtering condition to remove any 'null' values. If I'm correct, AC defaults empty long values to 0, hence:

I've also placed a condition to to fetch PK that 'is not empty.'

But can we also write a value where @id =! 'null'? Even though @id is a long (not string) datatype? As you can see, the @id is constrained to a long (not string) datatype:

How can we create an expression where @id != 'Null'?