IN Operator SQL

Question

I have a table called NUMS with a single column n.
And I fill values 1,2,3,4,5,null in it.

Now a query

SELECT n FROM Nums 
 WHERE n IN (1, 2,         


        

Answer 1

I am also comparing n with a null value which should yield unknown and it should return an empty set.

it shouldn't if you need in additional row filled with NULL values the best way imo is:

SELECT n FROM Nums WHERE n IN(1,2)
UNION
SELECT NULL

Now a query

SELECT n FROM Nums WHERE n NOT IN(1, 2, null)

...gets converted to:

Here what I said above works and it does not return anything.

thats right, because nothing can be equal to NULL and for NULL comparison IS NULL statement is used