Fetching Null Value from table

Question

I have a table where I am want to findout the total number of product (count of product) based on the ProdName.
I have the following table with two columns:
create table newproduct (prodid integer, prodname varchar(30));
Insert into newproduct values (100, 'TowerA')
Insert into newproduct values (160, 'TowerA')
Insert into newproduct values (170, 'TowerB')
Insert into newproduct values (120, 'TowerB')
Insert into newproduct values (140, 'TowerC')
Insert into newproduct values (180, '')
So here the query that I trying to use:
Select Distinct prodname from newproduct;
Select prodid from newproduct where prodname is null; /* Correct way */
Select prodid from newproduct where prodname in (''); /* I want result (180) by using this query */
How can I do it?

Answer 1

I'm not sure why you're trying to accomplish it that way, but you could try to use NVL to do that.
You just need to make sure whatever value you input in the NVL is something you won't ever obtain as a real column value.
Select prodid from newproduct where nvl(prodname, 'NULL VALUE HERE!') in ('NULL VALUE HERE!');Also, for performance reasons, since you're applying a function to the column, it won't be looking up indexes for matches, unless you create a function-based index.
Nulls are not indexed anyway, but I'm not sure what you're trying to do with this query.