I read that but is there a way to meet the above requirement. And I will like to add that IS NULL and IS NOT NULL should evaluate to true/false. These operators are made for this and should not be returning NULL.
> It should be noted that a check constraint is satisfied if the check expression evaluates to true or the null value. Since most expressions will evaluate to the null value if any operand is null, they will not prevent null values in the constrained columns. To ensure that a column does not contain null values, the not-null constraint described in the next section can be used.
